fixes build on archlinux/gcc/opencv4

[lennart]

note: you will also need to install the vtk package via package manager

maybe this should be added to the readme, however, I can only confirm compilation works on (current) archlinux (gcc10). Application starts, camera live-feed with color + laplace magnification tested and also riesz magnification for pre-recorded video-file

[bronekalmar]

In my archlinux setup, I needed to instal vtk and hdf5 packages via package manager.