[clang] [clang] Add `clang::behaves_like_std(...)` attribute (PR #76596)

[Max Winkler via cfe-commits]

MaxEW707 wrote:

> It's not ready, but I have a draft for a much more general attribute: #78071

I was playing around with your draft PR and I do prefer your solution over mine.
It will even help to cleanup my custom `xmmintrin.h` header that we have to reduce include times from SSE headers.

Let me know if you want me to close this our in favour of your PR.

https://github.com/llvm/llvm-project/pull/76596