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

https://github.com/ndowens/void-packages swig
https://github.com/void-linux/void-packages/pull/16045

swig: update to 4.0.1
SONAME: no change
Built a few packages against this version and no build errors

A patch file from https://github.com/void-linux/void-packages/pull/16045.patch is attached