Created by: wangkuiyi

When I was trying to fix cpplint errors, I traced into some CUDA-related macro definitions in our codebase:

https://github.com/PaddlePaddle/Paddle/blame/24509f4af942bb250564756ad636691c7921e1df/paddle/fluid/platform/variant.h#L17-L29

They look wired as they are not used in our codebase.