[semaphore] Fix mono_sem_wait() for Darwin, clean up mono_sem_post().

semaphore_wait() never returns -1, but returns KERN_ABORTED if the
call needs to be repeated.  This caused a semaphore wait to sometimes
return in the SGen workers code when it shouldn't, which caused a
mysterious assertion failure.

mono/utils/mono-semaphore.c

@@ -112,7 +112,7 @@ mono_sem_wait (MonoSemType *sem, gboolean alertable)
 #ifndef USE_MACH_SEMA
 	while ((res = sem_wait (sem)) == -1 && errno == EINTR)
 #else
-	while ((res = semaphore_wait (*sem)) == -1 && errno == EINTR)
+	while ((res = semaphore_wait (*sem)) == KERN_ABORTED)
 #endif
 	{
 		if (alertable)
@@ -131,9 +131,9 @@ mono_sem_post (MonoSemType *sem)
 #ifndef USE_MACH_SEMA
 	while ((res = sem_post (sem)) == -1 && errno == EINTR);
 #else
-	while ((res = semaphore_signal (*sem)) == -1 && errno == EINTR);
+	res = semaphore_signal (*sem);
 	/* OSX might return > 0 for error */
-	if (res != 0)
+	if (res != KERN_SUCCESS)
 		res = -1;
 #endif
 	return res;