[flang] Another SUBMODULE unparsing tweak, and restore buildability with gcc < 8.1

Original-commit: flang-compiler/f18@86b5db4b234da659702320a3c614f3f6b5ba3757
Reviewed-on: https://github.com/flang-compiler/f18/pull/130
Tree-same-pre-rewrite: false
2 files changed
tree: 72e44b2f969fe660f751daef04a34e17310ad653
  1. flang/