[libc-commits] [libc] [libc] Add an extension macro to get numerical thread id (PR #195202)

[Petr Hosek via libc-commits]

petrhosek wrote:

I share the concern @kaladron expressed in https://github.com/llvm/llvm-project/pull/195139#issuecomment-4378243281, that is if we provide this API, people will start relying on it which will make it more difficult to change things in the future ([Hyrum's law](https://www.hyrumslaw.com/)).

https://github.com/llvm/llvm-project/pull/195202