make: existence-only prerequisites (was: make: order-only prerequisites?)

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> I don't remember anything that just checks 'existance'
> without checking the timestamp.
Which, to epeat myself,  would be extremely useful, especially for directories
(because adding a file means updating the directories mtime, which ...).
I always end up with something like
	test -d ${d} || mkdir -p ${d}
which doesn't feel very make-like.