There is a new pull request by gcat432 against master on the void-packages repository

https://github.com/gcat432/void-packages crystal-0.31.1
https://github.com/void-linux/void-packages/pull/14858

crystal: update to 0.31.1.
- Compilation was locally tested with both i686 and x86_64
- Package was locally installed on x86_64, `crystal` and `shards` work good
- Issue with multi-threading: it is not possible to compile programs with the `-Dpreview_mt` flag. As said in #14688 a patch to `gc` is required for them to work, and we will eventually not bump this package until a new release which will contain this new feature.

**Note to Crystal developers:** If you really want to enable green threads support in the `gc` package, please use [this patch](https://gist.github.com/gcat432/2f7f000624c9333483e2a5b9abfba146) and compile `gc` (I did it using `xbps-src` using the same revision and force reinstalled it: it works without issue). Good luck!

A patch file from https://github.com/void-linux/void-packages/pull/14858.patch is attached