Remove clang workaround.

https://reviews.llvm.org/D58531 remains open, but allegedly (from the comments on that change) https://reviews.llvm.org/D58091 made it no longer matter...

Change-Id: If7c1e6aa51eccf9bfea6a06278ddb556a2de4396

Author: enh-google

libc/include/pthread.h

@@ -144,20 +144,7 @@ int pthread_cond_timedwait_monotonic_np(pthread_cond_t* _Nonnull __cond, pthread
                                         const struct timespec* _Nullable __timeout) __INTRODUCED_IN_64(28);
 int pthread_cond_wait(pthread_cond_t* _Nonnull __cond, pthread_mutex_t* _Nonnull __mutex);
 
-#if defined(__clang__)
-/*
- * Disable -Wbuiltin-requires-header because clang confuses this declaration with the one defined in
- * "llvm/tools/clang/include/clang/Basic/Builtins.def", which did not define any formal arguments.
- * It seems to be an upstream bug and the fix (https://reviews.llvm.org/D58531) is still under
- * review. Thus, let's disable the warning for this function declaration.
- */
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wbuiltin-requires-header"
-#endif
 int pthread_create(pthread_t* _Nonnull __pthread_ptr, pthread_attr_t const* _Nullable __attr, void* _Nonnull (* _Nonnull __start_routine)(void* _Nonnull), void* _Nullable);
-#if defined(__clang__)
-#pragma clang diagnostic pop
-#endif
 
 int pthread_detach(pthread_t __pthread);
 void pthread_exit(void* _Nullable __return_value) __noreturn;