If you try to build e17, the ebuild will check whether edje has been built with USE="png". But this doesn't make sense at all, as edje doesn't even offer such an USE-Flag. I think the e17 ebuild should rather check if evas respectively imlib2 have been built woth USE="png" enabled, if at all.
it should be checking evas ... edje was checked because it was the one failing when in reality it just needs underlying evas png loader
