Fix broken rmdir script
Fix broken rmdir script

Unfortunately, the removal shell script introduced in #10860 does not handle paths very well that dont exist, e.g.

* `find` runs before its `-exec` test, thus throws `find: "${path}": No such file or directory`
* it seem that `/bin/rmdir` is intended to break is certain cases, thus `-f` is not desired.
  so, if `${path}` does not exist, it'll still break, which is most likely not one of those cases.

This change reintroduces a check for existence. This way, it is ensured that there is actually
a directory to be removed when invoking the script.
vitorgalvao/brew,MikeMcQuaid/brew,claui/brew,Homebrew/brew,claui/brew,Homebrew/brew,MikeMcQuaid/brew,EricFromCanada/brew,JCount/brew,nandub/brew,sjackman/homebrew,vitorgalvao/brew,sjackman/homebrew,claui/brew,nandub/brew,JCount/brew,sjackman/homebrew,nandub/brew,JCount/brew,MikeMcQuaid/brew,sjackman/homebrew,Homebrew/brew,EricFromCanada/brew,EricFromCanada/brew,Homebrew/brew,claui/brew,EricFromCanada/brew,vitorgalvao/brew,nandub/brew,JCount/brew,MikeMcQuaid/brew,vitorgalvao/brew