We have to do this in order to ensure that an updated .gitlab-ci.yml is actually available on every release.

We do a release every day so we end up with a lot of "release commits"
(noise) in the master branch, which we don't want.

We can simply construct it ourselves.

This is expected of the new generic package API:
https://docs.gitlab.com/ee/user/packages/generic_packages/

GitLab 13.5 introduced support for one-dimensional matrices:
https://about.gitlab.com/releases/2020/10/22/gitlab-13-5-released/#allow-one-dimensional-parallel-matrices
Hopefully this works as intended. :)

See https://gitlab.com/gitlab-org/gitlab/-/issues/259663