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

[Joseph Huber via libc-commits]

jhuber6 wrote:

Okay I vaguely recall one niche use-case that this will break. Currently I build the RPC loader / server utilities in the main LLVM build similar to how we build `libc-hdrgen`. The minimum GCC compiler right now is 7.4 which doesn't support this https://godbolt.org/z/zaTvbz1os. These utilities include a handful of files, which I believe use `LIBC_HAS_BUILTIN` (like atomic.h). If someone were to build LLVM with an older GCC this would no longer work and it would error out.

This is technically out of scope of what we list as the minimum supported GCC version, but so far it's just been hacked around. We could potentially stipulate that people need to use newer `GCC`, but it's a little annoying when this worked around it previously.

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