[libc-commits] [libc] [libc] Implement CMPLX related macros (PR #156344)

[A. Jiang via libc-commits]

frederick-vs-ja wrote:

This caused libc++ CI failure with GCC. It seems that GCC can't correctly parse `typedef _Complex __float128 cfloat128;`, [Godbolt link](https://godbolt.org/z/vqqa5387P).

I'm trying to use `__typeof__` as a workaround.

https://github.com/llvm/llvm-project/pull/156344