[libcxx-commits] [libcxx] [llvm] [libc++] Optionally support filecheck-based tests (PR #165769)

[Louis Dionne via libcxx-commits]

ldionne wrote:

> It looks like the plan here is to find `FileCheck` (or a python equivalent) as a system dependency though? I think that should alleviate any concerns with circular dependencies/build times given it needs to only happen at CI image build time. Given that doesn't happen very often, I don't see how build times would be a concern either.

If a user wants to set up `FileCheck` locally to work on libc++, they shouldn't have to configure LLVM and build it. It's a fragile and complicated process. With this patch, they only need to do `pip install filecheck` and they're done.

If we productized `FileCheck` into something standalone that can be installed with e.g. Homebrew, I'd much prefer use the LLVM version. But since I don't see that happening, I think it makes more sense to use an easily installable equivalent of it.

https://github.com/llvm/llvm-project/pull/165769