Bootstrap Rust on Slackware using mrustc
Until recently, the only way to bootstrap rust was to download a precompiled rust stage0 compiler of the previous rust release and use it to compile the current release from source.
mrustc is an alternative rust compiler written in C++ which can be used to bootstrap rust completely from source (given you have a C++ compiler).
mrustc targets rust 1.19.0, so this script will build mrustc, use it to build a stage0 1.19.0 rust and stdlib, use this stage0 to build 1.20.0 from source (full-bootstrap) and using that step through each release up to the latest release, which is currently 1.39.0.