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

https://github.com/Johnnynator/void-packages bwrap
https://github.com/void-linux/void-packages/pull/25705

bubblewrap: use NetBSD realpath on musl 
In some cases bubbewrap calls realpath without having /proc available,
but musl's realpath requires /proc.

@ericonr  

A patch file from https://github.com/void-linux/void-packages/pull/25705.patch is attached