python3Packages.torch: gate NCCL with cudaSupport

Author: Connor Baker

pkgs/development/python-modules/torch/default.nix

@@ -273,7 +273,7 @@ in buildPythonPackage rec {
   PYTORCH_BUILD_VERSION = version;
   PYTORCH_BUILD_NUMBER = 0;
 
-  USE_NCCL = setBool (cudaPackages ? nccl);
+  USE_NCCL = setBool (cudaSupport && cudaPackages ? nccl);
   USE_SYSTEM_NCCL = setBool useSystemNccl;                  # don't build pytorch's third_party NCCL
   USE_STATIC_NCCL = setBool useSystemNccl;