[clang] [llvm] [clang][ci] Move libc++ testing into the main PR pipeline (PR #93318)

[Louis Dionne via llvm-commits]

================
@@ -54,3 +54,68 @@ cmake -S "${MONOREPO_ROOT}"/llvm -B "${BUILD_DIR}" \
 echo "--- ninja"
 # Targets are not escaped as they are passed as separate arguments.
 ninja -C "${BUILD_DIR}" -k 0 ${targets}
+
----------------
ldionne wrote:

It seems that we disagree on the approach taken here. I won't block you from merging the patch even though I think it's not the right approach, but I had to explain my thoughts on it.

> If you're willing to do the work in a reasonable time (remember we're reducing CI pressure here), you can take over this PR or I can abandon it. I personally had enough of bash scripting to iterate on this immediately.

I can't commit to that, I'm already overcommitted for libc++ work.

Like I said, while I think this is not a great approach, I won't block you from going forward with it. It does achieve better overall throughput for the CI pipeline, so it's not like this approach has no benefits at all.

https://github.com/llvm/llvm-project/pull/93318