[OE-core] Getting rid of "The license listed internal was not in the licenses collected" warnings?

[Mikko.Rapeli at bmw.de]

On Tue, Sep 08, 2015 at 12:19:51PM +0200, Mike Looijmans wrote:
> Ah, wait, on closer inspection it actually exists, but it's a symlink to
> some none-existing location. Apparently, to save some diskspace and reduce
> maintenance on text files I linked a few files together. Somehow, the link
> got copied instead of the file contents.
>
> I un-symlinked the "internal" file, and (together with some forced rebuilds)
> that finally made the warning go away.

Since I had similar stupid-user moments too, there is a generic function in
sanity tests to check for broken symlinks. Would be great if you could add
license files to this check.

-Mikko