Add nomnigraph include folder to `Caffe2_GPU_INCLUDE` (#37056)
Summary:
Because `caffe2/contrib/tensort` includes nomnigraph headers
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37056
Test Plan: `cmake ../pytorch -DPYTHON_EXECUTABLE=/usr/bin/python3.7 -DCMAKE_BUILD_TYPE=RELWITHDEBINFO -DUSE_CUDA=YES -DBUILD_TEST=YES -DUSE_TENSORRT=YES -DTENSORRT_ROOT=$HOME/Downloads/TensorRT-7.0.0.11 -DCMAKE_CXX_COMPILER=/usr/bin/cuda-g++ -DCMAKE_C_COMPILER=/usr/bin/cuda-gcc -DUSE_MKLDNN=ON -G Ninja; ninja torch_cuda`
Differential Revision: D21178927
Pulled By: malfet
fbshipit-source-id: e1bed94fdb395ebfd6eb5d950ca378da77592531
