message: Safe handling of dynamic_cast
  Clang (MacOS) seems to have problem w/ dynamic casting, hence just graciously skip this multi-control optimization.
diff: @@ -194,7 +194,8 @@ public:
  void visit(Circuit &in_circuit) override {
  // std::cout << "HOWDY: Visit quantum circuit: " << in_circuit.name() << "\n";
  - if (in_circuit.name() == "C-U") {
  + if (in_circuit.name() == "C-U" &&
  + dynamic_cast<xacc::quantum::ControlModifier *>(&in_circuit)) {
  auto *asControlledBlock =
  dynamic_cast<xacc::quantum::ControlModifier *>(&in_circuit);
  assert(asControlledBlock);
  