impl looks correct, generated header looks incorrect:
void * pthread_setspecific(pthread_key_t, const void *) __NOEXCEPT;
fix libc/include/pthread.yaml for pthread_setspecific should return int, not void*.
Otherwise the following error is observed when building libcxxabi against llvm-libc:
/llvm-project-main/build/include/c++/v1/__thread/support/pthread.h:216:10: error: cannot initialize return object of type 'int' with an rvalue of type 'void *'
216 | return pthread_setspecific(__key, __p);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~