Bug#917687: [3dprinter-general] Bug#917687: cura-engine: FTBFS: ./obj-x86_64-linux-gnu/CMakeFiles/CMakeTmp/./obj-x86_64-linux-gnu/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8: undefined reference to `pthread_create'

[Gregor Riepl]

> Looks OK to me.

Ok... So it turns out I made a stupid versioning mistake when preparing a
fixed version of libpolyclipping.
After fixing that and reinstalling the correct pkg-config file, I can build
cura-engine again.

I'll ask Petter to upload libpolyclipping-6.4.2-6 ASAP.