Build caffe2 with conda failed

I build the caffe2 with anaconda following the page.
In the server with a single titanx, has cudnn7 and cuda9 but do not have nccl, so I download the nccl2 from nvidia and extract it to path/to/local/nccl2, and then edit the ./pytorch/conda/integrated/ in the line 42 to be:“export NCCL_ROOT_DIR=path/to/local/nccl2”.
Then I need to use caffe2 with python2, so I added “conda_args+=(” --python 2.7") " in the ./pytorch/scripts/ to use python2.7.
The building was succeed, but when I run python2
from caffe2.python import core
It tells me:
WARNING:root:This caffe2 python run does not have GPU support. Will run in CPU only mode.
WARNING:root:Debug message: No module named caffe2_pybind11_state_hip
Segmentation fault (core dumped)

My question is:
a. why the conda does not support gpu?
b. if I am using a single gpu, is nccl necessary for building?
c. how to fix No module named caffe2_pybind11_state_hip

PyTorch or Caffe2: caffe2
How you installed PyTorch (conda, pip, source): conda
Build command you used (if compiling from source):./scripts/ --install-locally --cuda 9.0 --cudnn 7
PyTorch version:
Python version:2.7
CUDA/cuDNN version:9.1/7
GPU models and configuration:??
GCC version (if compiling from source):5.4.0
CMake version:not install
Versions of any other relevant libraries:
Thank you very much!