bug#49158: Add ruby-for-crystal.

[Maxim Cournoyer]

Hello,

"jgart" <jgart@dismail.de> writes:

> Hi Guix,
>
> We've (Ryan, David, Raghav, and others) started packaging crystal for guix: 
> https://crystal-lang.org/
>
> This patch adds an old version of ruby that is required by the crystal
> language bootstrap process. This is related to 49142.

Since the crystal-lang patches haven't landed in more than a year,
I think it's safer to punt on this.

Closing.

Thanks!

Maxim