Its job is to download the previous Rust release (beta for master, stable for beta and previous stable for current stable), including Cargo, build the build system with Cargo and start it.
The build system then builds native dependencies (LLVM) and runs Cargo several times for different components.
There is only one Python file: https://github.com/rust-lang/rust/blob/master/src/bootstrap/...
Its job is to download the previous Rust release (beta for master, stable for beta and previous stable for current stable), including Cargo, build the build system with Cargo and start it.
The build system then builds native dependencies (LLVM) and runs Cargo several times for different components.