Prepare yourself for a shock then; bootstrapping rustc starts from an already-built version of rustc[1]:
> the only way to build a modern version of rustc is a slightly less modern version.
(There is, at least theoretically, a non-circular bootstrap chain starting with a very old rustc written in OCaml, but the more practical alternative is probably to use mrustc[2] instead.)
[1] https://rustc-dev-guide.rust-lang.org/building/bootstrapping...