if you pretend that LLVM and friends are not part of the toolchain
So no need for LLVM and GCC, Great news!
Where can we download it?
Assuming you are serious, there is https://github.com/bytecodealliance/wasmtime/tree/main/crane... which is written in Rust and is targeted to become the default debug backend in rustc. LLVM has accumulated a lot of optimizations contributed by various groups and people over more than a decade. It's hard to catch up to that by virtue of resource limits.
I was being sarcastic, when Cranelift becomes the official reference implementation then I shut up.
Is there a reason to replace LLVM? Are there still memory bugs that are popping up and causing issues?