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

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> I looked into it in the past and couldn't figure out how to do it because FileCheck was pulling in stuff from LLVM support libraries.

Why would that matter when `FileCheck` ends up being statically linked?

> However, I would like not to block this improvement to our test suite on such a refactoring unless someone signs up to do it in the short term.

I don't think it should require any refactoring. Just a bit of packaging infrastructure. I can look into getting a pypi distributon setup.

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