(b)make: generating multiple targets at once

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

Is there a way to sanely express the following in a Makefile?

dst/foo depends on src/foo, dst/bar depends on src/bar etc.

gen foo bar will generate dst/foo from src/foo and dst/bar from src/bar (etc)

gen has a large one-time overhead, so gen foo bar ... is hugely preferrable 
to gen foo; gen bar; gen ...

It may be tolerable to call gen foo bar if only dst/foo is out-of-date, but 
it's not tolerable to call gen in case nothing is out-of-date.