Why not use LLD for linking Rust? You already must have the LLVM for Rust to be buildable, so that do not add any dependency.
LLD would work fine for the whole tree, and did previously, but is much much slower than mold which is why we switched to mold.
Having to build all dependencies of rust including python and openssl and everything else before being able to use mold erases most of the full-tree build speedups as the path to rust is already about 80% of the full tree build time.
We are a distro that mandates independently verified 100% deterministic builds from source for any given release commit of the tree, so we have to build the whole tree several times for every release.
C/C++ + libc ↓ LLVM/LLD ↓ mrustc + minicargo ↓ rustc 1.90 Cargo 1.90 ──→ OpenSSL ↓ Python x.py ↓ Rust 1.91+
My point though was that you already build many end-of-life projects just so they can be used in the build, mold2 can now one of those rather than being built for its use in the final distro.
Would that meant that building rust is slower, but everything else is the same, and you don't have to maintain a fork of another complex project?
Rust is the single most expensive thing to bootstrap in any given linux distro.
It is the thing you need mold the most for to speed things up.
Unfortunately Rust does not even do full source bootstrapped deterministic builds themselves. Their release strategy is entirely the honor system, where everyone trusts their pinky swear that a single computer or person will never be compromised and allow for the injection of malware into the binaries everyone downloads from rustup.
The only reason we have even the crazy long bootstrap path we have today at all is the hard work of mutabah, an individual independent hacker that does it as a hobby.
The rust team seemingly considers memory safety as the only security problem that matters, and supply chain attacks out of scope.