download_strategy: use tar xf.
download_strategy: use tar xf.

The flags and separate `-` aren't required on 10.5 which is the oldest
version of macOS we support (and it looks nicer this way).

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