Good luck. You'll need a cross compiler. There's a script in this repo called 'toolchain.sh' which will do it for you. I've tested it only on the vegas nodes, so it'll probably work. Probably.
Once you have the cross compiler set up and installed, and in your PATH, you can edit config.cfg to set options for the build.
To build, run 'make'. To test, run 'make test'. If you're using the x86 version, you may want to run 'QEMU_FLAGS="-enable-kvm" make test' to make it run faster.