Revert to building doxygen docs with autotools

Martin Langrequested to merge
ci-doxygen-docs-autotools into hotfix-16.1

Description

Revert to old way of building doxygen docs. The new CMake based version has some bug that causes doxygen to ignore all fortran files.

Checklist

  • I have checked that my code follows the Octopus coding standards
  • I have added tests for all the new features added in this request.

Merge request reports