Specify minimum OSX version

Author: hmaarrfk

recipe/meta.yaml

@@ -116,6 +116,7 @@ outputs:
         - ninja
         # avoid that people without GPUs needlessly download ~0.5-1GB
         - __cuda  # [cuda_compiler_version != "None"]
+        - __osx >={{ MACOSX_DEPLOYMENT_TARGET|default("10.9") }}  # [osx]
       run_constrained:
         # These constraints ensure conflict between pytorch and
         # pytorch-cpu 1.1 which we built before conda-forge had GPU infrastructure