German voice - Cepstral

[MrGlasspoole]

I need german and there are only this files i can find:
http://freeswitch.xpirio.com/

The problem is they need Cepstral:
https://freeswitch.org/confluence/display/FREESWITCH/mod_cepstral

But from that tutorial it seems like you have to rebuild/compile FreeSwitch?

I also tried this trick here (step 3):
https://junedmunshi.wordpress.com/tag/freeswitch-language-configuration/

But changing "vm/tts.xml" to "vm/sounds.xml" in "/de/vm/sounds.xml" does not work.