Dev env for OneFlow

To setup conda (只需要运行一次)
```
/usr/local/anaconda3/bin/conda init
```
To activate:
```
conda activate oneflow-dev-gcc7
```

Recommanded cmake args:

cmake .. \
    -DPython3_EXECUTABLE=$CONDA_PREFIX/bin/python3 \
    -DCUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda \
    -DCUDNN_ROOT_DIR=/usr/local/cudnn \
    -DBUILD_SHARED_LIBS=ON \
    -DTHIRD_PARTY_MIRROR=aliyun \
    -DBUILD_GIT_VERSION=OFF

其中 -DCUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda 和 -DCUDNN_ROOT_DIR=/usr/local/cudnn 可以根据实际需要调整

Zailiang/conda-env

Dev env for OneFlow