Simulator uses system ubuntu libopus lib instead of rockbox one

[bahus]

I tried to debug in Simulator one opus issue and got really upset unabling to break inside any libopus code and all my logging was ignored. So turns out this code is not used at all - instead system libopus lib is used. Could be caused by recent SDL2 migration (as it's pulled by libsndfile lib needed for SDL sound initialization)

Any way to make sure that rockbox libs are used? For now I renamed all opus entry methods to be able to debug rockbox libopus code.