[Build] Current build feature option "dev" would cause build failure.

## 🐛 Bug

## To Reproduce

Steps to reproduce the behavior:
run `bash script/build_dgl.sh -t dev`

This would cause error in the build stage of DGL:
```
cc1plus: all warnings being treated as errors
make[2]: *** [third_party/googletest/googletest/CMakeFiles/gtest.dir/build.make:76: third_party/googletest/googletest/CMakeFiles/gtest.dir/src/gtest-all.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:475: third_party/googletest/googletest/CMakeFiles/gtest.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
```

## Expected behavior

## Environment

- DGL Version (e.g., 1.0):
- Backend Library & Version (e.g., PyTorch 0.4.1, MXNet/Gluon 1.3):
- OS (e.g., Linux):
- How you installed DGL (`conda`, `pip`, source):
- Build command you used (if compiling from source):
- Python version:
- CUDA/cuDNN version (if applicable):
- GPU models and configuration (e.g. V100):
- Any other relevant information:

## Additional context