This is the code for a research project for a Forth native code compiler done in the 1990s. The only working target for this compiler is MIPS. You can find an overview and the papers about it through http://www.complang.tuwien.ac.at/projects/rafts.html. I don't think the code is stable enough for building on it, but maybe you can glean something useful from it.
This code contains a version of burg that can produce Forth output. Use
burg -F
to get Forth output.