Auto merge of #81451 - nikic:llvm-12, r=nagisa

Upgrade to LLVM 12

This implements the necessary adjustments to make rustc work with LLVM 12. I didn't encounter any major issues so far.

r? `@cuviper`

29 files changed, 124 insertions, 9 deletions

diff --git a/src/ci/docker/host-x86_64/arm-android/Dockerfile b/src/ci/docker/host-x86_64/arm-android/Dockerfile
index f675252fb16..43cdbbe92e3 100644
--- a/src/ci/docker/host-x86_64/arm-android/Dockerfile
+++ b/src/ci/docker/host-x86_64/arm-android/Dockerfile
@@ -36,5 +36,8 @@ ENV SCRIPT python3 ../x.py --stage 2 test --host='' --target $TARGETS
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 COPY scripts/android-start-emulator.sh /scripts/
 ENTRYPOINT ["/scripts/android-start-emulator.sh"]
diff --git a/src/ci/docker/host-x86_64/dist-aarch64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-aarch64-linux/Dockerfile
index 95c54ca1abc..e6b6b6e53b9 100644
--- a/src/ci/docker/host-x86_64/dist-aarch64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-aarch64-linux/Dockerfile
@@ -24,6 +24,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/aarch64-unknown-linux-gnueabi/bin
 
 ENV CC_aarch64_unknown_linux_gnu=aarch64-unknown-linux-gnueabi-gcc \
diff --git a/src/ci/docker/host-x86_64/dist-android/Dockerfile b/src/ci/docker/host-x86_64/dist-android/Dockerfile
index 258dcea06e6..ee727359f39 100644
--- a/src/ci/docker/host-x86_64/dist-android/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-android/Dockerfile
@@ -36,3 +36,6 @@ ENV SCRIPT python3 ../x.py dist --host='' --target $TARGETS
 
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
+
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
diff --git a/src/ci/docker/host-x86_64/dist-arm-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-arm-linux/Dockerfile
index 88b13eab2d0..1be3fecd88f 100644
--- a/src/ci/docker/host-x86_64/dist-arm-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-arm-linux/Dockerfile
@@ -27,6 +27,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/arm-unknown-linux-gnueabi/bin
 
 ENV CC_arm_unknown_linux_gnueabi=arm-unknown-linux-gnueabi-gcc \
diff --git a/src/ci/docker/host-x86_64/dist-armhf-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-armhf-linux/Dockerfile
index 977ef08c274..66eb4137a87 100644
--- a/src/ci/docker/host-x86_64/dist-armhf-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-armhf-linux/Dockerfile
@@ -19,6 +19,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/arm-unknown-linux-gnueabihf/bin
 
 ENV CC_arm_unknown_linux_gnueabihf=arm-unknown-linux-gnueabihf-gcc \
diff --git a/src/ci/docker/host-x86_64/dist-armv7-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-armv7-linux/Dockerfile
index 65d713359d9..c13f63911f8 100644
--- a/src/ci/docker/host-x86_64/dist-armv7-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-armv7-linux/Dockerfile
@@ -19,6 +19,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/armv7-unknown-linux-gnueabihf/bin
 
 ENV CC_armv7_unknown_linux_gnueabihf=armv7-unknown-linux-gnueabihf-gcc \
diff --git a/src/ci/docker/host-x86_64/dist-i586-gnu-i586-i686-musl/Dockerfile b/src/ci/docker/host-x86_64/dist-i586-gnu-i586-i686-musl/Dockerfile
index c734202eef6..c98fc7dcfff 100644
--- a/src/ci/docker/host-x86_64/dist-i586-gnu-i586-i686-musl/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-i586-gnu-i586-i686-musl/Dockerfile
@@ -30,6 +30,9 @@ RUN CC=gcc CFLAGS="-m32 -Wa,-mrelax-relocations=no" \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV RUST_CONFIGURE_ARGS \
       --musl-root-i586=/musl-i586 \
       --musl-root-i686=/musl-i686 \
diff --git a/src/ci/docker/host-x86_64/dist-i686-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-i686-linux/Dockerfile
index 22d7cbb0d14..247b539652b 100644
--- a/src/ci/docker/host-x86_64/dist-i686-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-i686-linux/Dockerfile
@@ -68,11 +68,13 @@ RUN ./build-binutils.sh
 COPY host-x86_64/dist-x86_64-linux/build-gcc.sh /tmp/
 RUN ./build-gcc.sh && apt-get remove -y gcc g++
 
-# Debian 6 has Python 2.6 by default, but LLVM needs 2.7+
 COPY host-x86_64/dist-x86_64-linux/build-python.sh /tmp/
-RUN ./build-python.sh
+# Build Python 2.7 needed for Clang 10.
+RUN ./build-python.sh 2.7.12
+# Build Python 3 needed for LLVM 12.
+RUN ./build-python.sh 3.9.1
 
-# LLVM needs cmake 3.4.3 or higher, and is planning to raise to 3.13.4.
+# LLVM needs cmake 3.13.4 or higher.
 COPY host-x86_64/dist-x86_64-linux/build-cmake.sh /tmp/
 RUN ./build-cmake.sh
 
diff --git a/src/ci/docker/host-x86_64/dist-mips-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-mips-linux/Dockerfile
index cb5c17c25ab..b0f06569a9c 100644
--- a/src/ci/docker/host-x86_64/dist-mips-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-mips-linux/Dockerfile
@@ -21,6 +21,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV HOSTS=mips-unknown-linux-gnu
 
 ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
diff --git a/src/ci/docker/host-x86_64/dist-mips64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-mips64-linux/Dockerfile
index 31146e3ead4..245c28e1fa3 100644
--- a/src/ci/docker/host-x86_64/dist-mips64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-mips64-linux/Dockerfile
@@ -20,6 +20,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV HOSTS=mips64-unknown-linux-gnuabi64
 
 ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
diff --git a/src/ci/docker/host-x86_64/dist-mips64el-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-mips64el-linux/Dockerfile
index dadd50a7e66..03998c8880a 100644
--- a/src/ci/docker/host-x86_64/dist-mips64el-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-mips64el-linux/Dockerfile
@@ -21,6 +21,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV HOSTS=mips64el-unknown-linux-gnuabi64
 
 ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
diff --git a/src/ci/docker/host-x86_64/dist-mipsel-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-mipsel-linux/Dockerfile
index d2d65565b10..58617270621 100644
--- a/src/ci/docker/host-x86_64/dist-mipsel-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-mipsel-linux/Dockerfile
@@ -20,6 +20,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV HOSTS=mipsel-unknown-linux-gnu
 
 ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
diff --git a/src/ci/docker/host-x86_64/dist-powerpc-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-powerpc-linux/Dockerfile
index 651daac8613..ecaa495e97a 100644
--- a/src/ci/docker/host-x86_64/dist-powerpc-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-powerpc-linux/Dockerfile
@@ -25,6 +25,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/powerpc-unknown-linux-gnu/bin
 
 ENV \
diff --git a/src/ci/docker/host-x86_64/dist-powerpc64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-powerpc64-linux/Dockerfile
index 6ff4d787212..a22d9a7553e 100644
--- a/src/ci/docker/host-x86_64/dist-powerpc64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-powerpc64-linux/Dockerfile
@@ -26,6 +26,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/powerpc64-unknown-linux-gnu/bin
 
 ENV \
diff --git a/src/ci/docker/host-x86_64/dist-powerpc64le-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-powerpc64le-linux/Dockerfile
index c1a621ff105..5157dd4c79b 100644
--- a/src/ci/docker/host-x86_64/dist-powerpc64le-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-powerpc64le-linux/Dockerfile
@@ -25,6 +25,9 @@ RUN ./build-powerpc64le-toolchain.sh
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV \
     AR_powerpc64le_unknown_linux_gnu=powerpc64le-linux-gnu-ar \
     CC_powerpc64le_unknown_linux_gnu=powerpc64le-linux-gnu-gcc \
diff --git a/src/ci/docker/host-x86_64/dist-riscv64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-riscv64-linux/Dockerfile
index dff7c475157..80b7793cb7e 100644
--- a/src/ci/docker/host-x86_64/dist-riscv64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-riscv64-linux/Dockerfile
@@ -19,6 +19,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/riscv64-unknown-linux-gnu/bin
 
 ENV CC_riscv64gc_unknown_linux_gnu=riscv64-unknown-linux-gnu-gcc \
diff --git a/src/ci/docker/host-x86_64/dist-s390x-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-s390x-linux/Dockerfile
index 1b261993cfc..5e626243952 100644
--- a/src/ci/docker/host-x86_64/dist-s390x-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-s390x-linux/Dockerfile
@@ -25,6 +25,9 @@ USER root
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/s390x-ibm-linux-gnu/bin
 
 ENV \
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile
index 8413d775ac4..121dd3f455a 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile
@@ -23,6 +23,9 @@ RUN /tmp/freebsd-toolchain.sh x86_64
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV \
     AR_x86_64_unknown_freebsd=x86_64-unknown-freebsd11-ar \
     CC_x86_64_unknown_freebsd=x86_64-unknown-freebsd11-clang \
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile
index 2a0f6a39c57..c2e44ead51e 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile
@@ -22,6 +22,9 @@ RUN bash /tmp/illumos-toolchain.sh x86_64 gcc
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV \
     AR_x86_64_unknown_illumos=x86_64-illumos-ar \
     CC_x86_64_unknown_illumos=x86_64-illumos-gcc \
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
index d1b4bbf7fff..4dd4378f196 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
@@ -68,11 +68,13 @@ RUN ./build-binutils.sh
 COPY host-x86_64/dist-x86_64-linux/build-gcc.sh /tmp/
 RUN ./build-gcc.sh && apt-get remove -y gcc g++
 
-# Debian 6 has Python 2.6 by default, but LLVM needs 2.7+
 COPY host-x86_64/dist-x86_64-linux/build-python.sh /tmp/
-RUN ./build-python.sh
+# Build Python 2.7 needed for Clang 10.
+RUN ./build-python.sh 2.7.12
+# Build Python 3 needed for LLVM 12.
+RUN ./build-python.sh 3.9.1
 
-# LLVM needs cmake 3.4.3 or higher, and is planning to raise to 3.13.4.
+# LLVM needs cmake 3.13.4 or higher.
 COPY host-x86_64/dist-x86_64-linux/build-cmake.sh /tmp/
 RUN ./build-cmake.sh
 
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/build-python.sh b/src/ci/docker/host-x86_64/dist-x86_64-linux/build-python.sh
index c172b978112..970d67b6db3 100755
--- a/src/ci/docker/host-x86_64/dist-x86_64-linux/build-python.sh
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/build-python.sh
@@ -3,7 +3,8 @@
 set -ex
 source shared.sh
 
-curl https://www.python.org/ftp/python/2.7.12/Python-2.7.12.tgz | \
+VERSION=$1
+curl https://www.python.org/ftp/python/$VERSION/Python-$VERSION.tgz | \
   tar xzf -
 
 mkdir python-build
@@ -12,10 +13,10 @@ cd python-build
 # Gotta do some hackery to tell python about our custom OpenSSL build, but other
 # than that fairly normal.
 CFLAGS='-I /rustroot/include' LDFLAGS='-L /rustroot/lib -L /rustroot/lib64' \
-    hide_output ../Python-2.7.12/configure --prefix=/rustroot
+    hide_output ../Python-$VERSION/configure --prefix=/rustroot
 hide_output make -j10
 hide_output make install
 
 cd ..
 rm -rf python-build
-rm -rf Python-2.7.12
+rm -rf Python-$VERSION
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile
index 904ee64db3b..08f07eb8284 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile
@@ -20,6 +20,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 
 WORKDIR /build/
 
+# Build cmake before musl toolchain, as we replace the compiler during that step.
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 COPY scripts/musl-toolchain.sh /build/
 # We need to mitigate rust-lang/rust#34978 when compiling musl itself as well
 RUN CFLAGS="-Wa,-mrelax-relocations=no -Wa,--compress-debug-sections=none -Wl,--compress-debug-sections=none" \
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile
index f3f7255f154..92bdc9811fd 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile
@@ -9,6 +9,9 @@ RUN /tmp/build-netbsd-toolchain.sh
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV PATH=$PATH:/x-tools/x86_64-unknown-netbsd/bin
 
 ENV \
diff --git a/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile b/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile
index 0e28ea9668f..0182ebb8b59 100644
--- a/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile
+++ b/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile
@@ -20,6 +20,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 RUN mkdir -p /config
 RUN echo "[rust]" > /config/nopt-std-config.toml
 RUN echo "optimize = false" >> /config/nopt-std-config.toml
diff --git a/src/ci/docker/host-x86_64/i686-gnu/Dockerfile b/src/ci/docker/host-x86_64/i686-gnu/Dockerfile
index 195601755f3..feaab819bdd 100644
--- a/src/ci/docker/host-x86_64/i686-gnu/Dockerfile
+++ b/src/ci/docker/host-x86_64/i686-gnu/Dockerfile
@@ -20,6 +20,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV RUST_CONFIGURE_ARGS --build=i686-unknown-linux-gnu
 # Exclude some tests that are unlikely to be platform specific, to speed up
 # this slow job.
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-aux/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-aux/Dockerfile
index a5bedadc05b..00ad7b0a710 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-aux/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-aux/Dockerfile
@@ -42,5 +42,8 @@ RUN npm install browser-ui-test -g --unsafe-perm=true
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV RUST_CONFIGURE_ARGS --build=x86_64-unknown-linux-gnu
 ENV RUST_CHECK_TARGET check-aux-and-gui
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-distcheck/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-distcheck/Dockerfile
index 5faa0ccab56..09d9cda02bd 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-distcheck/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-distcheck/Dockerfile
@@ -19,6 +19,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 ENV RUST_CONFIGURE_ARGS --build=x86_64-unknown-linux-gnu --set rust.ignore-git=false
 ENV SCRIPT python3 ../x.py --stage 2 test distcheck
 ENV DIST_SRC 1
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
index 89171a6f215..d4838c0d6f8 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
@@ -18,6 +18,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
 COPY host-x86_64/x86_64-gnu-tools/checktools.sh /tmp/
 
 ENV RUST_CONFIGURE_ARGS \
diff --git a/src/ci/docker/scripts/cmake.sh b/src/ci/docker/scripts/cmake.sh
new file mode 100755
index 00000000000..70096173403
--- /dev/null
+++ b/src/ci/docker/scripts/cmake.sh
@@ -0,0 +1,34 @@
+#!/bin/bash
+set -ex
+
+hide_output() {
+  set +x
+  on_err="
+echo ERROR: An error was encountered with the build.
+cat /tmp/build.log
+exit 1
+"
+  trap "$on_err" ERR
+  bash -c "while true; do sleep 30; echo \$(date) - building ...; done" &
+  PING_LOOP_PID=$!
+  "$@" &> /tmp/build.log
+  trap - ERR
+  kill $PING_LOOP_PID
+  rm /tmp/build.log
+  set -x
+}
+
+# LLVM 12 requires CMake 3.13.4 or higher.
+# This script is not necessary for images using Ubuntu 20.04 or newer.
+CMAKE=3.13.4
+curl -L https://github.com/Kitware/CMake/releases/download/v$CMAKE/cmake-$CMAKE.tar.gz | tar xzf -
+
+mkdir cmake-build
+cd cmake-build
+hide_output ../cmake-$CMAKE/configure
+hide_output make -j$(nproc)
+hide_output make install
+
+cd ..
+rm -rf cmake-build
+rm -rf cmake-$CMAKE