[llvm] Revert "Reapply "[CI] Migrate to runtimes build"" (PR #145742)

[Nathan Gauër via llvm-commits]

Keenuts wrote:

> I don’t really understand how this fixes it. The error is with clang-tools-extra which was built before this patch too. This patch just changes the runtime builds shouldn’t impact the check-clang-tools target.

I don't think this fixes it, but seems like this hides it (not great)


> I would also prefer to avoid reverting this if possible. The tight interaction between clang and libcxx made this a pain to land and to reland (three libcxx patches and one LWG issue required).

> It’s also a race condition (seemingly), so how have you validated that everything works as expected?

Yes, the more I dig the more I think this is an actual race condition. I was able to reproduce on an older LLVM commit, but not all the time.




https://github.com/llvm/llvm-project/pull/145742