So I successfully hacked my python stuff to create jars, and to do so for python 2.5, too. Testing it in the MozillaBuildRC1, here’s time make -C browser chrome for the current code and my new hack:
real 0m21.812s user 0m20.731s sys 0m11.761s
vs.
real 0m10.375s user 0m9.028s sys 0m5.158s
from scratch. The numbers don’t change significantly if you run them again, which is to be expected, as most files are preprocessed and overwritten anyway.