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

https://github.com/ahesford/void-packages fontconfig
https://github.com/void-linux/void-packages/pull/32794

fontconfig: move default configuration to INSTALL/REMOVE
Encoding /etc/fonts/conf.d configuration symlinks in the package means that upgrades and installations will clobber existing custom configurations. In addition, removing any default configuration files would cause xbps-pkgdb to complain.

Managing default configurations in INSTALL/REMOVE allows custom configurations to persist through upgrades and removals. A guard file, /etc/fonts/conf.d/.autoconfig, serves as an INSTALL guard to prevent configuration modifications during upgrade. It also stores a list of the default configurations that will be removed when the package is uninstalled. This is an extension of an idea from @ericonr.

These scripts should mimic existing behavior through the first subsequent upgrade or installation.

A patch file from https://github.com/void-linux/void-packages/pull/32794.patch is attached