As pointed out here:
https://mail-archives.apache.org/mod_mbox/incubator-general/201907.mbox/%3CF9383AEE-5693-40ED-BE1C-C109F3D219B7%40classsoftware.com%3E

There is a file in Nvidia cub submodule with a license that does not allow redistribution:https://github.com/NVlabs/cub/blob/v1.8.0/test/half.h

This will prevent MXNet from using it. While I raised an issue on NVlab github, I would propose the following if there is no response

1. change submodule cub to use v1.7.4 instead of v1.8, 1.7.4 and older does not have this file:
   https://github.com/NVlabs/cub/tree/v1.7.4/test. Not sure if v1.7.4 has the historical problems that lead us to make a snap shot of it

2. revert Change CUB submodule to track Nvidia CUB project. #13322 which will go back to use dmlc/cub and it's v1.7 without the file.

cc @frankfliu