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

https://github.com/ericonr/void-packages proM
https://github.com/void-linux/void-packages/pull/25135

projectM: split into -devel subpackage.
Also fix location of desktop files, and assign to LDFLAGS instead of
adding to it.

@abenson 

A patch file from https://github.com/void-linux/void-packages/pull/25135.patch is attached