Don't set HOMEBREW_MACOS_VERSION on non-mac systems
Don't set HOMEBREW_MACOS_VERSION on non-mac systems

mgrimes/brew,Homebrew/brew,claui/brew,sjackman/homebrew,vitorgalvao/brew,MikeMcQuaid/brew,JCount/brew,Linuxbrew/brew,DomT4/brew,MikeMcQuaid/brew,claui/brew,DomT4/brew,hanxue/linuxbrew,DomT4/brew,sjackman/homebrew,maxim-belkin/brew,konqui/brew,mahori/brew,mgrimes/brew,maxim-belkin/brew,mahori/brew,EricFromCanada/brew,sjackman/homebrew,EricFromCanada/brew,reitermarkus/brew,alyssais/brew,sjackman/homebrew,reitermarkus/brew,Linuxbrew/brew,claui/brew,ilovezfs/brew,Homebrew/brew,mahori/brew,reitermarkus/brew,nandub/brew,Linuxbrew/brew,maxim-belkin/brew,claui/brew,hanxue/linuxbrew,EricFromCanada/brew,MikeMcQuaid/brew,vitorgalvao/brew,JCount/brew,Linuxbrew/brew,hanxue/linuxbrew,nandub/brew,alyssais/brew,EricFromCanada/brew,konqui/brew,mgrimes/brew,konqui/brew,JCount/brew,nandub/brew,reitermarkus/brew,nandub/brew,DomT4/brew,ilovezfs/brew,vitorgalvao/brew,alyssais/brew,vitorgalvao/brew,mahori/brew,MikeMcQuaid/brew,Homebrew/brew,ilovezfs/brew,Homebrew/brew,konqui/brew,JCount/brew