message: Change optimization mode name for swift IRGen.
diff: @@ -1178,7 +1178,7 @@ unsigned SwiftExpressionParser::Parse(DiagnosticManager &diagnostic_manager,
  m_swift_ast_context->GetLanguageOptions().EnableThrowWithoutTry = true;
  }
  - m_swift_ast_context->GetIRGenOptions().Optimize = false;
  + m_swift_ast_context->GetIRGenOptions().OptMode = swift::OptimizationMode::NoOptimization;
  m_swift_ast_context->GetIRGenOptions().Verify =
  false; // normally we'd like to verify, but unfortunately the verifier's
  // error mode is abort().
  