@idiot >WHO CAME UP WITH THIS FUCKING HORSESHIT?
People who need to compile everything from scratch (no, really)
Rust doesn't officially support compiling itself from scratch if you don't already have a rust compiler. And with how often the language changes, they only test that previous minor version can compile the next one, so unless you're feeling brave, that's what building from source does everywhere.
Anyways, next time you end up in the situation of needing to compile rust from scratch, just download a binary package for the one-before-current rust version and use it to compile the current one. Just like you'd bootstrap a C compiler. If you do gentoo just to get -march native for everything you're not gonna miss out on anything except heating by doing that.