New comment by Duncaen on void-packages repository

https://github.com/void-linux/void-packages/issues/35410#issuecomment-1084662772

Comment:
Its simply not how xbps-src works, the core idea is that builds happen in clean and reproducible environments and not on the host system.

If you really want to build packages using xbps-src in docker without allowing nested namespaces and uid maps, check how the github CI is setup, by creating temporary containers containing the build environment and invoke xbps-src in a way that it allows to use the container as build environment.
https://github.com/void-linux/void-packages/blob/master/.github/workflows/build.yaml