There is a new pull request by sgn against master on the void-packages repository

https://github.com/sgn/void-packages fix-mpc-qt-ftbfs
https://github.com/void-linux/void-packages/pull/27920

mpc-qt: fix ftbfs
Fetch the latest version of qthelper.hpp from mpv.
See https://github.com/mpv-player/mpv/commit/575197ff8b0a0d8cd14f7ee78461c1d61d045d72

A patch file from https://github.com/void-linux/void-packages/pull/27920.patch is attached