message: Lower CUDA Compute Capability limit
  Enoki (& optix) are compatible starting from NVIDIA Maxwell series (=CUDA CC 5.0). Tested.
diff: @@ -12,7 +12,7 @@ option(ENOKI_AUTODIFF "Build Enoki automatic differentation library?" OFF)
  option(ENOKI_PYTHON "Build pybind11 interface to CUDA & automatic differentiation libraries?" OFF)
  if (ENOKI_CUDA)
  - set(ENOKI_CUDA_COMPUTE_CAPABILITY "61" CACHE STRING "Compute capability as specified by https://developer.nvidia.com/cuda-gpus")
  + set(ENOKI_CUDA_COMPUTE_CAPABILITY "50" CACHE STRING "Compute capability as specified by https://developer.nvidia.com/cuda-gpus")
  set(CMAKE_CUDA_FLAGS "${CMAKE_CUDA_FLAGS} -gencode arch=compute_${ENOKI_CUDA_COMPUTE_CAPABILITY},code=compute_${ENOKI_CUDA_COMPUTE_CAPABILITY} -cudart shared")
  if (NOT WIN32)
  set(CMAKE_CUDA_FLAGS "${CMAKE_CUDA_FLAGS} -Xcompiler -fvisibility=hidden")
  