[libcxx-commits] [libcxx] [libc++] Move lerp to its own header instead of <cmath> (PR #213111)

[A. Jiang via libcxx-commits]

frederick-vs-ja wrote:

Looks like we should add `std::lerp` here (as a quick fix).
https://github.com/llvm/llvm-project/blob/27e6d832069729d75a76e7776737bf4477dde5a8/libcxx/utils/libcxx/test/modules.py#L71-L76

Also, we need to include `<__type_traits/promote.h>` in `<complex>`.

https://github.com/llvm/llvm-project/pull/213111