* Use runners on HPC instead of fake.

* This can occor when make is terminated abnormally.

* Specifically, flang-new adds a totally new level by formatting
  free-form into fixed-form source along the way.

* On FreeBSD, g++ might also be available under the name g++${VERSION}.

* The initial commit d5b1f26f omitted the distribution
  rule in Makefile.am.

* The version currently available via Alpine Linux are all affected by
  a bug that leads to non-resolved references.
* Doxygen versions 1.9.5 to 1.11.0 exhibit the buggy behaviour.
* Will switch back to doxygen CI-Container once 1.12 or newer is
  installed there.