containers: Add cirrus-run container
This tool can be used to trigger Cirrus CI jobs from outside of Cirrus CI itself, and we're going to use it to add FreeBSD and macOS support to our GitLab CI configurations by delegating them.
This tool can be used to trigger Cirrus CI jobs from outside of Cirrus CI itself, and we're going to use it to add FreeBSD and macOS support to our GitLab CI configurations by delegating them.