message: More verbose logging.
  Summary:
  Log the method whose virtual scope is empty when we crash for that reason.
  Also introduce newlines between trace output for interface scopes.
diff: @@ -889,13 +889,13 @@ void ClassScopes::build_interface_scopes() {
  }
  for (const auto& meth : intf_cls->get_vmethods()) {
  const auto& scopes = m_sig_map[meth->get_name()][meth->get_proto()];
  - always_assert(!scopes.empty()); // at least the method itself
  + // at least the method itself
  + always_assert_log(!scopes.empty(), "Scope empty for %s", SHOW(meth));
  auto& intf_scope = m_interface_scopes[intf_it.first];
  intf_scope.push_back({});
  for (const auto& scope : scopes) {
  if (scope.interfaces.count(intf_it.first) == 0) continue;
  - TRACE_NO_LINE(
  - VIRT, 9, "add interface scope for %s", SHOW(intf_it.first));
  + TRACE(VIRT, 9, "add interface scope for %s", SHOW(intf_it.first));
  intf_scope.back().push_back(&scope);
  }
  }
  