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

[Guillaume Chatelet via llvm-commits]

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@@ -166,7 +172,7 @@ LIBC_INLINE void atomic_thread_fence([[maybe_unused]] MemoryOrder mem_ord) {
 // except no instructions for memory ordering are issued. Only reordering of
 // the instructions by the compiler is suppressed as order instructs.
 LIBC_INLINE void atomic_signal_fence([[maybe_unused]] MemoryOrder mem_ord) {
-#if LIBC_HAS_BUILTIN(__atomic_signal_fence)
+#if __has_builtin(__atomic_signal_fence)
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gchatelet wrote:

AFAICT it does
https://godbolt.org/z/ojcfTTcdM

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