Change "-Wmaybe-uninitialized" to warning

src/goto-symex/complexity_limiter.cpp

@@ -98,6 +98,7 @@ bool complexity_limitert::are_loop_children_too_complicated(
   // complicated, we make sure we don't execute it the other 17 times. But as
   // soon as we're running the loop again via a different context it gets a
   // chance to redeem itself.
+#pragma GCC diagnostic warning "-Wmaybe-uninitialized"
   optionalt<std::reference_wrapper<lexical_loopst::loopt>> loop_to_blacklist;
   for(auto frame_iter = current_call_stack.rbegin();
       frame_iter != current_call_stack.rend();