[Windows] Fix torch_cuda's forced link (#35659)
Summary:
The current config on `master` yields the following errors when build from source on Windows with CMake and Visual Studio 2019.
```
Severity Code Description Project File Line Suppression State
Error LNK2001 unresolved external symbol \?warp_size@cuda@at@YAHXZ\ torch D:\AI\pytorch\build_libtorch\caffe2\LINK 1
Severity Code Description Project File Line Suppression State
Error LNK1120 1 unresolved externals torch D:\AI\pytorch\build_libtorch\bin\Release\torch.dll 1
Severity Code Description Project File Line Suppression State
Error LNK2001 unresolved external symbol \?warp_size@cuda@at@YAHXZ\ caffe2_observers D:\AI\pytorch\build_libtorch\modules\observers\LINK 1
Severity Code Description Project File Line Suppression State
Error LNK1120 1 unresolved externals caffe2_observers D:\AI\pytorch\build_libtorch\bin\Release\caffe2_observers.dll 1
Severity Code Description Project File Line Suppression State
Error LNK2001 unresolved external symbol \?warp_size@cuda@at@YAHXZ\ caffe2_detectron_ops_gpu D:\AI\pytorch\build_libtorch\modules\detectron\LINK 1
Severity Code Description Project File Line Suppression State
Error LNK1120 1 unresolved externals caffe2_detectron_ops_gpu D:\AI\pytorch\build_libtorch\bin\Release\caffe2_detectron_ops_gpu.dll 1
```
This change at least fixes the above errors in that specific setting. Do you think it makes sense to get this merged or will it break other settings?
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35659
Differential Revision: D20735907
Pulled By: ezyang
fbshipit-source-id: eb8fa1e69aaaa5af2da3a76963ddc910bb716479
