This adds the rust toolchain 1.46.0: https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1460-2020-08-27 Because rustc-1.46.0 enables static PIE by default for `x86_64-unknown-linux-musl` this release will suffer from: https://github.com/NixOS/nixpkgs/issues/94228 So this commit doesn't remove the 1.45.2 release. This commit also specifies the right LLVM packages to use for each rust release.