Support AMD hardware

[eyalroz]

At the moment, this runner will only work with NVIDIA GPUs: It requires the CUDA toolkit and driver, and will expect NVIDIA/CUDA's OpenCL library.

We should, instead, make it CMake-configurable, buildable and usable with only AMD hardware. At first, we can continue to require the presence of the CUDA Toolkit, but we also need to provide support for AMD's OpenCL driver/library/stack, in particularl when both are available on the system. Later we might consider allowing builds without CUDA altogether.