There's a merged pull request on the void-packages repository

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

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

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Or just remove this package, I dun know