avr-libc has not been broken, and in particular did not have a
kris incorrectly stated this in the BROKEN field, even though I've
been repeatedly telling him that it's actually been netpbm that broke
some time ago (apparently due to an upgraded C compiler in the
system; generating transparent PNGs caused it to dump core).
Fortunately, dinoex now updated the netpbm port, so all works again.