Rust was bootstrapped with an OCaml based compiler. Alas I don't think it has been kept up to date, so you won't be able to use it to compile the v1.0 source. Not sure how many generations in between the last OCaml compilable rust and the current rust you'd need to compile to bootstrap, probably quite a few.
Re:Announcing Rust 1.0
by steveklabnik on Friday May 15, 2015 @04:39PM
(#9553549)
Very, very, very many. https://github.com/rust-lang/rust/blob/master/src/snapshots....
I've still thought about doing it.
A while back, somebody got Cargo running on an unsupported platform, but bootstrapping was a major problem. The compiler had to bootstrap newer versions of itself tens of times, and that was only for a few weeks of breaking changes …
Part of the problem with this is that since it's a bootstrapped compiler, and the only one for the language so far, "downloading source" mean you need a binary to compile it with, which devolves to the same problem.