To my knowledge, extensions without dependencies simply have no dep file.
The audit script does not presently throw up a signal when there is an empty dep file, I may add that in.
Not to pick on Arslan in his absence, but it seems that the empty dep files mainly belong to his stuff upon a quick glance. I imagine that his build script echoes entries into the dep files, and when there are no deps then an empty dep file is created by echoing " ", perhaps.