mac: doesn't have pthread_condattr_setclock()

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/os/os-mac.h b/os/os-mac.h
index e4c2bc8..aec30f9 100644
--- a/os/os-mac.h
+++ b/os/os-mac.h
@@ -29,7 +29,6 @@
 #define FIO_USE_GENERIC_RAND
 #define FIO_HAVE_GETTID
 #define FIO_HAVE_CHARDEV_SIZE
-#define FIO_HAVE_PTHREAD_CONDATTR_SETCLOCK
 
 #define OS_MAP_ANON		MAP_ANON