os.rb: Do not load os/mac.rb with tests --generic
os.rb: Do not load os/mac.rb with tests --generic

hanxue/linuxbrew,rwhogg/brew,Linuxbrew/brew,maxim-belkin/brew,hanxue/linuxbrew,rwhogg/brew,maxim-belkin/brew,maxim-belkin/brew,Linuxbrew/brew,Linuxbrew/brew,rwhogg/brew,hanxue/linuxbrew,Linuxbrew/brew