Switch to rust-lang-nursery/compiler-builtins

This commit migrates the in-tree `libcompiler_builtins` to the upstream version
at https://github.com/rust-lang-nursery/compiler-builtins. The upstream version
has a number of intrinsics written in Rust and serves as an in-progress rewrite
of compiler-rt into Rust. Additionally it also contains all the existing
intrinsics defined in `libcompiler_builtins` for 128-bit integers.

It's been the intention since the beginning to make this transition but
previously it just lacked the manpower to get done. As this PR likely shows it
wasn't a trivial integration! Some highlight changes are:

* The PR rust-lang-nursery/compiler-builtins#166 contains a number of fixes
  across platforms and also some refactorings to make the intrinsics easier to
  read. The additional testing added there also fixed a number of integration
  issues when pulling the repository into this tree.

* LTO with the compiler-builtins crate was fixed to link in the entire crate
  after the LTO process as these intrinsics are excluded from LTO.

* Treatment of hidden symbols was updated as previously the
  `#![compiler_builtins]` crate would mark all symbol *imports* as hidden
  whereas it was only intended to mark *exports* as hidden.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/ci/init_repo.sh b/src/ci/init_repo.sh
index 817ed8dd554..f8e86986f82 100755
--- a/src/ci/init_repo.sh
+++ b/src/ci/init_repo.sh
@@ -67,13 +67,14 @@ for module in $modules; do
         mv "src/llvm-$commit" src/llvm
         continue
     fi
-    if [ ! -d "$cache_src_dir/$module" ]; then
+    if [ ! -e "$cache_src_dir/$module/.git" ]; then
         echo "WARNING: $module not found in pristine repo"
-        retry sh -c "git submodule deinit -f $module && git submodule update --init $module"
+        retry sh -c "git submodule deinit -f $module && \
+            git submodule update --init --recursive $module"
         continue
     fi
     retry sh -c "git submodule deinit -f $module && \
-        git submodule update --init --reference $cache_src_dir/$module $module"
+        git submodule update --init --recursive --reference $cache_src_dir/$module $module"
 done
 
 travis_fold end update_submodules