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

vpnc: change upstream to fork
https://github.com/void-linux/void-packages/pull/28320

Description:
fixes #26798.

* Changes upstream to https://github.com/streambinder/vpnc/. That's a fork
  that's a fork which is at least used in alpine.
* Depends on vpnc-scripts. New upstream doesn't ship those files anymore
* Add wrapper script to stay backwards compatible
* Switch to build_style=gnu-makefile instead of manually calling make.