install transformers in CI

.github/workflows/build.yml

@@ -25,7 +25,7 @@ jobs:
         run: |
           pip config set global.index-url https://pypi.tuna.tsinghua.edu.cn/simple
           pip install -U pip setuptools wheel --user
-          pip install pytest tensorboard deepspeed apex
+          pip install pytest tensorboard deepspeed apex transformers
       - uses: actions/checkout@v2
       - name: Install Colossal-AI      
         run: |