In brief, the following line in the DEPEND list for the pingus ebuild needs to be modified: media-libs/sdl-mixer -> media-libs/sdl-mixer[mod,modplug] (Or whatever the correct syntax is.) I built pingus today and it installed fine, but it had no music, because it couldn't play its own Impulse Tracker music files. But after I reinstalled the sdl-mixer package with the "mod" and "modplug" flags enabled (modplug required mod) the music in pingus worked just fine. These flag requirements should be added to the pingus dependency requirements, because it is pretty lame playing the game without music. Reproducible: Always
added a music use flag.
