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

https://github.com/toluschr/void-packages add-gamemode
https://github.com/void-linux/void-packages/pull/20653

New package: gamemode-1.5.1
I had nothing else to do, so I fetched Hyper-KVM's PR (#20424), added the lutris patch and made the changes requested by @Duncaen and @Chocimier

A patch file from https://github.com/void-linux/void-packages/pull/20653.patch is attached