There's a closed pull request on the void-packages repository

move update-check out of xbps-src
https://github.com/void-linux/void-packages/pull/31602

Description:
Continue discussion from #31546 

It's better to rewrite in a real programming language, however this is enough for now.

TODO: check only distfiles.

The `eval` step should be removed when we can remove all variable except `pkgname` and `version` from `distfiles`, and merge the first `distfiles` to the same line of `distfiles=`

@void-linux/pkg-committers 
@the-maldridge moving out of `xbps-src`, we can drop the weird `XBPS_ALLOW_CHROOT_BREAKOUT=yes` from `update-check` container.