[libcxx-commits] [libcxx] [libc++][test] Enhance `ADDITIONAL_COMPILE_FLAGS` to work with MSVC (PR #74974)

[Stephan T. Lavavej via libcxx-commits]

StephanTLavavej wrote:

I've reverted the `verify-support` changes, renamed `any-clang-or-gcc` => `gcc-style-warnings` and `msvc-cl-exe` => `cl-style-warnings`, and updated the PR description.

In the Python script, I've left `_isAnyClangOrGCC` unchanged, since that's what it's physically checking for. Let me know if you want that renamed too.

https://github.com/llvm/llvm-project/pull/74974