The homebrew installation for macos tasks takes 1min+ in each test run. We could instead do a separate homebrew install in a directory, and populate it from cache. Relveant .cirrus.yml piece:
https://github.com/postgres/postgres/blob/master/.cirrus.yml#L260

Docs for cirrus-ci cache stuff: https://cirrus-ci.org/guide/writing-tasks/#cache-instruction