I haven't gotten around to adjusting the parts needed for the R606 to run on macOS yet.
If you want it to try to run it there, you'll need to make an adjustment to use the R606 branch:
curl -o cgminer.rb "https://raw.githubusercontent.com/vthoang/homebrew-cgminer/master/cgminer.rb"
edit the cgminer.rb file and change branch from 'master' to 'r606'
followed with:
brew install --build-from-source ./cgminer.rb
I'll get around to testing that when the branch gets merged back. At which point it should mostly fix itself.