[openadk] various enhancements via gogs

Hi, I’ve submitted a rather large patchset via GOGS, see https://gogs.waldemar-brodkorb.de/oss/openadk/pulls/16 <https://gogs.waldemar-brodkorb.de/oss/openadk/pulls/16> Please let me know if you have any questions, or if you’d prefer to split the PR into thematically grouped parts (e.g. build time speedups, additional packages, etc…) Cheers, Diez