Usually you port by cross compiling an initial compiler, and bootstrapping from there.

Speaking from personal experience, that can be quite painful. Being able to build rust and cargo, even if only for bootstrapping when porting, would truly be a wondrous thing.

Why, we could always use emscripten to compile rustc to JavaScript and use that for bootstrapping!

On a more serious note, ghc at least solved this problem by allowing you to compile Haskell to C (-fvia-C). Writing a naive C code generator from whatever your backend is using is probably not that hard.

I actually did steveklabnik said porting ghc to alpine linux. Lets just say, ghc's cross compilation can be frustrating.

Forgot a what in there, just woke up me can not english.

Or by making use of an interpreter as first stage.

Go bootstrap uses Go1.4 which compiler is written in C. So: compile Go1.4 and use that to compile the Go 1.X compiler (I don't know but multiple steps might be necessary).