[libc-commits] [libc] [libc] use LIBC_HAS_BUILTIN instead __has_builtin (PR #82377)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 approved this pull request.

The GPU has `__has_builtin`, that's a `clang` thing, see https://godbolt.org/z/1MPozEor1. However, we are supposed to be consistent with the `LIBC_` prefixed stuff.

https://github.com/llvm/llvm-project/pull/82377