Check if VecGeom was built with CUDA support

[bernhardmgruber]

I just tried setting up AdePT and it nicely told me that I needed to have an installation of VecGeom with GDML enabled. I fixed that and then I got these errors:

CMake Error at test/CMakeLists.txt:8 (add_executable):
  Target "test_sparsevector_cpu" links to target
  "VecGeom::vecgeomcuda_static" but the target was not found.  Perhaps a
  find_package() call is missing for an IMPORTED target, or an ALIAS target
  is missing?
Call Stack (most recent call first):

It seems I also need to enable CUDA when building/installing VecGeom. It would be nice if there was a similar error/warning as with GDML support :)