When submitting a job via the git.sr.ht integration, the source repo is cloned even if the
sources key is omitted or set to the empty list.
When omitted, it's good that the default behavior is to clone the sources as that's what most developers would expect I guess.
But when it's explicitly set to the empty list, the repo being pushed to should not be added to the manifest. It's a waste of time, network use and disk space.