Fix attempt to donate priority within lock acquisition w/ S

src/threads/synch.c

@@ -226,6 +226,7 @@ lock_acquire (struct lock *lock)
   if (lock->holder != NULL)
     {
       t->waiting_lock = lock;
+      donate_priority (t, lock->holder);
     }
 
   sema_down (&lock->semaphore);