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

New package: qwtplot3d-0.2.7+svn191+gcc7
https://github.com/void-linux/void-packages/pull/23848

Description:
Qt/OpenGL-based C++ library, providing 3D-widgets for programmers

http://qwtplot3d.sourceforge.net/

This is the exact version that has been in debian for ages, it also matches the version in arch (although they call it r259 the source code is exactly the same).

I built this because I thought it was needed for GoldenCheetah (#23839), in the end it's not required (maybe optional).