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

https://github.com/pullmoll/void-packages xf86-input-synaptics
https://github.com/void-linux/void-packages/pull/26890

xf86-input-synaptics: fix build w/ musl-1.2.1
Graceful transition to 64 bit time.

A patch file from https://github.com/void-linux/void-packages/pull/26890.patch is attached