There is an updated pull request by CameronNemo against master on the void-packages repository

https://github.com/CameronNemo/void-packages libslirp
https://github.com/void-linux/void-packages/pull/20335

New package: libslirp-4.2.0
Draft for now, until slirp4netns 1.0 is released.

A patch file from https://github.com/void-linux/void-packages/pull/20335.patch is attached