This is okay because we only allow fast-forward merges, changes always
go through MRs, and MRs are subject to, e.g., the code quality checks.
This change is desirable because it should save some time and energy.
GitLab doesn't seem to have built-in support for this because of course
it doesn't.
To do this, we move the job scripts to a different file to make it
possible to share code between job scripts.