@raphael-proust I implemented the following of your suggestions:
- show artifact URLs directly in the logs
- configurable targets for the build, test, doc stages (in particular, an empty variable skips the corresponding step)
I made some progress the _build caching issue, thanks to a tip from (my informer) @ejgallego who had the exact same issue for Coq. The permissions of some files are changed when restored from cache. Unfortunately the only way I can reproduce the issue is by using dune to build a problematic directory, any attempt at a simpler reproduction has failed so far. But this does seem to be a Gitlab issue.