bug#70794: 30.0.50; Add Rust compilation regex

[Stefan Kangas]

Mattias Engdegård <mattias.engdegard@gmail.com> writes:

> Even with the obvious fixes, the pattern would still be incomplete and not 
> even match parts of the examples given. I'm happy to work with Rust users or 
> package maintainers to work out details but I don't want to do a rush job 
> now, nor delay Emacs 30.

BTW, shouldn't stuff like this be happier if it was in something like
`rust-mode`?

It seems like the maintainers of major modes are in a better position to
add and maintain support for the compilers and tools of their respective
languages than we are.