Allow separate directories for cuda and cudnn

[dsfenn]

I'm working on a cluster that has cuda and cudnn installed in different locations. I don't have write permission to these locations, so I can't change how they're laid out. CUDA.jl successfully finds the cuda location, but it looks in the same place for cudnn and thinks it's not installed because it can't find it there. I can't figure out how to change that.

If there is a way to specify a separate cudnn directory, I haven't been able to find it. If there isn't, it would be helpful to have.

[maleadt]

Make sure those directories are part of the library search path (LD_LIBRARY_PATH), which your cluster's module management system probably ought to do. That should do the job. CUDA_HOME etc is a common shortcut, but generally libraries and binaries you want to use should just be available on standard paths, and CUDA.jl shouldn't be looking all across the system for them.