Cache - staticpublisher errors

[ss23]

From http://open.silverstripe.org/ticket/4459

Cache building doesn't work if you've got a Redirector Page to external resource (SS 2.3.2)

It would try to create a file in cache folder with name: " http://yourlinkhere.com/blabla/" (Actually it will treat "/" as directories, and fail to create it! (Comes with error cannot create file)