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

https://github.com/Chocimier/void-packages-org postgresql-libs-devel
https://github.com/void-linux/void-packages/pull/23528

postgresql12: fix cross building of dependent packages
Fixes building few packages, rest still to test.

A patch file from https://github.com/void-linux/void-packages/pull/23528.patch is attached