Enforce universal binary check only for Homebrew/core
Enforce universal binary check only for Homebrew/core

Also, prefer `if` to `unless`.

MikeMcQuaid/brew,nandub/brew,JCount/brew,MikeMcQuaid/brew,JCount/brew,JCount/brew,Homebrew/brew,Homebrew/brew,EricFromCanada/brew,MikeMcQuaid/brew,nandub/brew,EricFromCanada/brew,MikeMcQuaid/brew,JCount/brew,nandub/brew,Homebrew/brew,nandub/brew,EricFromCanada/brew,EricFromCanada/brew,Homebrew/brew