Conda/OpenCE cudatoolkit-dev

[ptheywood]

Latest OpenCE builds using CUDA 11.8, which is not installed centrally.

To build things with a matching version, can install the cudatoolkit-dev package from conda to get the same version, which will be usable as long as the GPU driver is new enough.

It may be useful to add this to the cuda and openCE pages.

Also worth checking if the cudatoolkit-dev package sets CUDA_HOME and other env vars which may be depended upon, and if not add instructions on how to set them in the conda env (conda env config vars set CUDA_HOME=$(which nvcc)/../?)