In ebuild groupadd is called which doesn't exist on FreeBSD. The proper way for FreeBSD is "pw group add <group>". I would write the patch for ebuild but don't know what's the best way of checking OS. Reproducible: Always Steps to Reproduce:
It was my mistake. My CHOST was totally fucked up. Sorry about this. It works like a charm now.
marking invalid as per original reporter's comment