Disable homebrew cleanup on MacOS CI
brew cleanup saves disk space by deleting old versions of packages.
From time to time, CI MacOS images get out of date with Homebrew, and auto-cleanup is triggered unintentionally upon
brew install during a CI run.
There is no benefit to this on CI.
Disable Homebrew auto cleanup
by setting environment variable
On GitHub Actions, this is accomplished near the top of the particular .github/workflows/*.yml file:
env: HOMEBREW_NO_INSTALL_CLEANUP: 1