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

https://github.com/ndowens/void-packages graphviz
https://github.com/void-linux/void-packages/pull/18264

graphviz: update to 2.42.2.
Tested build on all that depends on this. Found valadoc uses pkg-config to find libgvc, in which CMakeList.txt from graphviz does not create. Added patch to install the pkg-config files needed and added link to math for gvc and pathplan.

I have submitted this patch upstream for hopeful merge.

A patch file from https://github.com/void-linux/void-packages/pull/18264.patch is attached