Cask: add doctor check for xattr
Cask: add doctor check for xattr

CC: Homebrew/homebrew-cask#69660

vitorgalvao/brew,Homebrew/brew,claui/brew,vitorgalvao/brew,JCount/brew,mahori/brew,claui/brew,nandub/brew,nandub/brew,konqui/brew,nandub/brew,sjackman/homebrew,vitorgalvao/brew,sjackman/homebrew,reitermarkus/brew,konqui/brew,nandub/brew,MikeMcQuaid/brew,sjackman/homebrew,reitermarkus/brew,EricFromCanada/brew,EricFromCanada/brew,JCount/brew,sjackman/homebrew,konqui/brew,mahori/brew,EricFromCanada/brew,JCount/brew,mahori/brew,EricFromCanada/brew,reitermarkus/brew,reitermarkus/brew,MikeMcQuaid/brew,Homebrew/brew,JCount/brew,MikeMcQuaid/brew,claui/brew,Homebrew/brew,mahori/brew,claui/brew,vitorgalvao/brew,Homebrew/brew,konqui/brew,MikeMcQuaid/brew