[libc-commits] [libc] [libc] Remove obsolete LIBC_HAS_BUILTIN macro (PR #86554)

[Schrodinger ZHU Yifan via libc-commits]

SchrodingerZhu wrote:

But `7.4.0` does not support `-std=c++20` anyway (which is added somewhere in our codebase)

https://github.com/llvm/llvm-project/pull/86554