ci: Stop setting CI_OVERRIDE_SHELL environment variable

This will render the src/ci/exec-with-shell.py script more or less
useless, but we're going to replace that by just using the system bash
instead.

Signed-off-by: Kristofer Rye <[email protected]>

Author: rye

src/ci/scripts/install-msys2.sh

@@ -23,6 +23,19 @@ if isWindows; then
     mkdir -p "$(ciCheckoutPath)/msys2/home/${USERNAME}"
     ciCommandAddPath "$(ciCheckoutPath)/msys2/usr/bin"
 
-    echo "switching shell to use our own bash"
-    ciCommandSetEnv CI_OVERRIDE_SHELL "$(ciCheckoutPath)/msys2/usr/bin/bash.exe"
+    # Detect the native Python version installed on the agent. On GitHub
+    # Actions, the C:\hostedtoolcache\windows\Python directory contains a
+    # subdirectory for each installed Python version.
+    #
+    # The -V flag of the sort command sorts the input by version number.
+    native_python_version="$(ls /c/hostedtoolcache/windows/Python | sort -Vr | head -n 1)"
+
+    # Make sure we use the native python interpreter instead of some msys equivalent
+    # one way or another. The msys interpreters seem to have weird path conversions
+    # baked in which break LLVM's build system one way or another, so let's use the
+    # native version which keeps everything as native as possible.
+    python_home="/c/hostedtoolcache/windows/Python/${native_python_version}/x64"
+    cp "${python_home}/python.exe" "${python_home}/python3.exe"
+    ciCommandAddPath "C:\\hostedtoolcache\\windows\\Python\\${native_python_version}\\x64"
+    ciCommandAddPath "C:\\hostedtoolcache\\windows\\Python\\${native_python_version}\\x64\\Scripts"
 fi