Well, I'm not here to claim that Rust's compile times aren't comparatively long, especially for non-incremental builds. It's a trade-off that was chosen to not need a runtime environment, nor be as simplistic/footgun as C.

What I'm saying is that this trade-off was chosen and continues to be popular, because the vast majority of users will never notice (nor will programmers really, as they have incremental builds).
Maybe you can download the fully built package from somewhere? Maybe Arch can package it in the proper repos?