[libcxx-commits] [libcxx] [libc++][test] Replace uses of `_LIBCPP_ABI_MICROSOFT` in tests (PR #77233)

[Mark de Wever via libcxx-commits]

https://github.com/mordante approved this pull request.

LGTM modulo one nit.

https://github.com/llvm/llvm-project/pull/77233