Seems to be because I've been playing with different upstream releases of Kodi in my tree. I've dropped that commit and rebased my tree. Do a "git fetch origin && git reset --hard origin/emu" and then rebuild. If you don't wanna rebuild everything do a "touch build*/.stamps/*/* before building. I'll put up new images soon.
EDIT: New images uploaded for both Generic/RPi, tested working.
EDIT2: I've added the dosbox fork from http://github.com/duganchen to the latest builds. It has SDL2 and mt32 support among other things. Included in RPi2/Generic image, run like this: "systemctl stop kodi && SDL_AUDIODRIVER=alsa dosbox -fullscreen && systemctl stop kodi"