Dir.glob too liberal when no lib folder

[techbelly]

If there's no lib folder in the folder in which you run 'gem this' s.files gets set to something like Dir.glob("{}/*/"). Then, when you run rake s.files will get set to every file on your machine - or least rake will hang until it runs out of memory.

[lazyatom]

Fixed glob so that if none of the expected directories are there, the
Rakefile doesn't crap out. Closed by cb86401