I'm currently working on a wesnoth 1.6.5 port to maemo 5 (n900), and found that the sdl_mixer library that come with maemo5 do not support ogg, while wesnoth require it. So i did build my own sdl_mixer library, and i wonder if i can upload this build to the extra devel repo, without breaking the current one in our device. Any help on this would be appreciated

Don't do that. There is already static library (libsdl-mixeroggwav1.2-dev) with ogg and wav support.