The idea is that any CUDA path can be OFF, and the corresponding tests shouldn't run
Unset/Uninitialized CUDA path != OFF; OFF means explicit exclude of the corresponding tests, whereas unset path implies the need for implicit searching for the corresponding path first
[ToDo] Refactor CUDA_TOOLKIT_ROOT_DIR
[ToDo] Separate GL tests - the only tests which need CUDA Samples for GL/glew.h
OFF, and the corresponding tests shouldn't runCUDA_TOOLKIT_ROOT_DIRGL/glew.h