It seems that the .gitlab-ci.yml did not trigger properly when the file
was changed last time, and now it does in this MR. Fix the file to make
it pass.
pmbootstrap now allows APKBUILDs in arbitrarily nested directories
within pmaports. This means that we really need some checks to ensure
APKBUILDs don't end up all over the place.
Add a test case with a whitelist of allowed directories.
Having this list in pmaports allows changing it without a new pmbootstrap
release.