How to compile Jonesforth on OSX Mojave?

Attempting to compile Jonesforth on OSX throws:

jonesforth.S:1154:10: fatal error: 'asm/unistd.h' file not found".

So I tried this advice for Linux, but still complains.

This Power PC port throws other exceptions, like:

invalid instruction mnemonic 'bctr'unexpected token in memory operand

Is there an OSX port around?