bug#70794: 30.0.50; Add Rust compilation regex

[Eli Zaretskii]

> From: Mattias Engdegård <mattias.engdegard@gmail.com>
> Date: Mon, 3 Jun 2024 18:22:48 +0200
> Cc: spacibba@aol.com,
>  70794@debbugs.gnu.org
> 
> > If you revert it, please fix this ASAP and install the results, since
> > I'd like to have this on the emacs-20 branch, which will be cut
> > soon-ish.
> 
> Personally I strongly prefer no rule to a broken one, or even to 
> Mattias's-best-guess-of-what-a-correct-rule-might-look-like.

Fine by me (I don't use Rust), but is the rule really broken?  What
happens if you move it to the end?