Comment 11 for bug 1945364

We don't implement OPTIMIZATION_NODE and TARGET_OPTION_NODE streaming:

    case OPTIMIZATION_NODE:
    case TARGET_OPTION_NODE:
      // FIXME: Our representation for these two nodes is a cache of
      // the resulting set of options. Not a record of the options
      // that got changed by a particular attribute or pragma. Should
      // we record that, or should we record the diff from the command
      // line options? The latter seems the right behaviour, but is
      // (a) harder, and I guess could introduce strangeness if the
      // importer has set some incompatible set of optimization flags?
      gcc_unreachable ();
      break;