Cross compiling generic things

I have a MiniPV and to measure the produced energy I use the Schelly 1PM. In the EnergyView this is displayed as a consumer. Now my idea was to create a generic device of type smartmeterproducer to map the Shelly to a smartmeterproducer. Unfortunately I can’t manage to compile or cross compile the generic devices. Is there a tutorial for this?

The website should have documentation for that, yes.

Btw, the way, the generic things have been split to a separate repository: