Compiling mustang programs with Nix

[jordanisaacs]

I just wanted to share that I was able to get mustang programs compiling & running on Nix through crate2nix. It works by leveraging Nix's cross compilation support & the buildRustCrate function to generate a mustang sysroot. It currently requires using this branch for correct parsing of the vendor field.

The sysroot and build support functions can be found here.
And the app build function is here.

For some more details on how it works see my notes. It probably won't make much sense unless you are proficient with crate2nix.