gitlab-ci: A few refactorings for ease of manual use
Previously it was quite inconvenient to use ci.sh on Darwin boxen. Fix this by moving more logic into ci.sh.
Due to a large amount of spam we do not allow new users to create repositories, they are "external" users. If you are a new user and want to create a repository, for example for forking GHC, open a new issue on ghc/ghc using the "get-verified" issue template
Previously it was quite inconvenient to use ci.sh on Darwin boxen. Fix this by moving more logic into ci.sh.