Transcode mp3's to ogg

[verhoevenv]

MP3's are not easily supported due to legal constraints. It's a serious pain to get the libraries on all platforms (that's what I'm currently struggling with on Mac). The libraries are often instable. So let's ditch the MP3s, ogg works just fine.

[nsajko]

See the upstream FAQ:
https://xiph.org/flac/faq.html#general__native_vs_ogg

Which should I use, (native) FLAC or Ogg FLAC?
The short answer right now is probably "native FLAC". If all you are
doing is compressing audio to be played back later, native FLAC will do
everything you need, is more widely supported, and will yield smaller
files. If you plan to edit the compressed audio, or want to multiplex
the audio with video later in an Ogg container, Ogg FLAC is a better
choice.

[Enet4]

If choosing between FLAC and OGG is that much of an issue, we can just try both and compare.