bug#70794: 30.0.50; Add Rust compilation regex

[Eli Zaretskii]

> From: Mattias Engdegård <mattias.engdegard@gmail.com>
> Date: Mon, 3 Jun 2024 16:54:02 +0200
> Cc: Eli Zaretskii <eliz@gnu.org>,
>  70794@debbugs.gnu.org
> 
> In fact the added pattern has visibly wrecked the display of 
> etc/compilation.txt so I'm taking the slightly drastic step of reverting it. 
> It seems we'll need to work harder on this one -- sorry.

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.

Thanks.