Cirrus CI: add a simple CI using BSD Commit: https://github.com/vim/vim/commit/e307073680d498b113c7df8250abd5676de1ed13 Author: Christian Brabandt <cb@256bit.org> Date: Wed Nov 27 15:45:57 2019 +0100 Cirrus CI: add a simple CI using BSD Cirrus CI allows to run CI tests in a wide variety of systems, such as Mac, Windows and FreeBSD. For a starter, add a Cirrus-CI test just for FreeBSD using version 12, assuming Windows and Linux are already tested using appveyor and Travis CI