[clang] [Clang] Add constexpr eval for cmath builtins (PR #194327)

[Timm Baeder via cfe-commits]

tbaederr wrote:

What? I can't review the things I have no idea about.

https://llvm.org/docs/CodeReview.html#code-reviews-speed-and-reciprocity

> Ping the patch. If it is urgent, provide reasons why it is important to you to get this patch landed and ping it every couple of days. If it is not urgent, **the common courtesy ping rate is one week**. Remember that you’re asking for valuable time from other professional developers.

https://github.com/llvm/llvm-project/pull/194327