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

update barrier to 2.3.3
https://github.com/void-linux/void-packages/pull/24367

Description:
Upstream moved to a git submodule for gtest and gmock. I took https://github.com/void-linux/void-packages/blob/master/srcpkgs/wabt/template as an example how to download and move gtest to the proper location.

This works for me locally. Let me know if anything needs changing.