See https://github.com/openjdk/jdk/blob/09514745fc87d5a212bdf09399aa2045f02b4612/src/hotspot/share/cds/archiveBuilder.cpp#L489

bool ArchiveBuilder::is_excluded(Klass* klass) {
  ...
  } else if (klass->is_objArray_klass()) {
    if (DynamicDumpSharedSpaces) {
      // Don't support archiving of array klasses for now (WHY???)
      return true;
    }
   ...