Rollup merge of #66569 - pietroalbini:gha-1, r=alexcrichton

GitHub Actions: preparations, part 1

This PR adds the first batch of commits in preparation for GitHub Actions:

* Added GitHub Actions support in `src/ci/shared.sh` and bootstrap.
* Addded a `setup-environment.sh` script which guesses and sets the `DEPLOY`, `DEPLOY_ALT` and `IMAGE` environment variables automatically, to reduce the verbosity of the CI configuration.

This PR does **not** yet add any builders on GitHub Actions.

r? @alexcrichton

3 files changed, 35 insertions, 4 deletions

diff --git a/src/ci/scripts/install-mingw.sh b/src/ci/scripts/install-mingw.sh
index 8b579587b9e..98373df7fce 100755
--- a/src/ci/scripts/install-mingw.sh
+++ b/src/ci/scripts/install-mingw.sh
@@ -52,7 +52,7 @@ if isWindows; then
     if [[ "${CUSTOM_MINGW-0}" -ne 1 ]]; then
         pacman -S --noconfirm --needed mingw-w64-$arch-toolchain mingw-w64-$arch-cmake \
             mingw-w64-$arch-gcc mingw-w64-$arch-python2
-        ciCommandAddPath "${SYSTEM_WORKFOLDER}/msys2/mingw${bits}/bin"
+        ciCommandAddPath "$(ciCheckoutPath)/msys2/mingw${bits}/bin"
     else
         mingw_dir="mingw${bits}"
 
diff --git a/src/ci/scripts/install-msys2.sh b/src/ci/scripts/install-msys2.sh
index ce37c3b1469..c9fafc7fe6b 100755
--- a/src/ci/scripts/install-msys2.sh
+++ b/src/ci/scripts/install-msys2.sh
@@ -12,8 +12,8 @@ IFS=$'\n\t'
 source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
 
 if isWindows; then
-    choco install msys2 --params="/InstallDir:${SYSTEM_WORKFOLDER}/msys2 /NoPath" -y --no-progress
-    mkdir -p "${SYSTEM_WORKFOLDER}/msys2/home/${USERNAME}"
+    choco install msys2 --params="/InstallDir:$(ciCheckoutPath)/msys2 /NoPath" -y --no-progress
+    mkdir -p "$(ciCheckoutPath)/msys2/home/${USERNAME}"
 
-    ciCommandAddPath "${SYSTEM_WORKFOLDER}/msys2/usr/bin"
+    ciCommandAddPath "$(ciCheckoutPath)/msys2/usr/bin"
 fi
diff --git a/src/ci/scripts/setup-environment.sh b/src/ci/scripts/setup-environment.sh
new file mode 100755
index 00000000000..e126a06edab
--- /dev/null
+++ b/src/ci/scripts/setup-environment.sh
@@ -0,0 +1,31 @@
+#!/bin/bash
+# This script guesses some environment variables based on the builder name and
+# the current platform, to reduce the amount of variables defined in the CI
+# configuration.
+
+set -euo pipefail
+IFS=$'\n\t'
+
+source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
+
+# Builders starting with `dist-` are dist builders, but if they also end with
+# `-alt` they are alternate dist builders.
+if [[ "${CI_JOB_NAME}" = dist-* ]]; then
+    if [[ "${CI_JOB_NAME}" = *-alt ]]; then
+        echo "alternate dist builder detected, setting DEPLOY_ALT=1"
+        ciCommandSetEnv DEPLOY_ALT 1
+    else
+        echo "normal dist builder detected, setting DEPLOY=1"
+        ciCommandSetEnv DEPLOY 1
+    fi
+fi
+
+# All the Linux builds happen inside Docker.
+if isLinux; then
+    if [[ -z "${IMAGE+x}" ]]; then
+        echo "linux builder detected, using docker to run the build"
+        ciCommandSetEnv IMAGE "${CI_JOB_NAME}"
+    else
+        echo "a custom docker image is already set"
+    fi
+fi