[Feature] Move 'Install MMCV' to a independent CI item.

.github/workflows/build.yml

@@ -37,19 +37,26 @@ jobs:
         include:
           - torch: 1.3.0+cpu
             torchvision: 0.4.1+cpu
+            torch_version: 1.3.0
           - torch: 1.5.0+cpu
             torchvision: 0.6.0+cpu
+            torch_version: 1.5.0
           - torch: 1.5.0+cu101
             torchvision: 0.6.0+cu101
+            torch_version: 1.5.0
+            cuda_version: 101
           - torch: 1.6.0+cu101
             torchvision: 0.7.0+cu101
+            torch_version: 1.6.0
+            cuda_version: 101
           - torch: 1.7.0+cu101
             torchvision: 0.8.1+cu101
+            torch_version: 1.7.0
+            cuda_version: 101
           - torch: 1.8.0+cu101
             torchvision: 0.9.0+cu101
-          - torch: 1.8.0+cu101
-            torchvision: 0.9.0+cu101
-
+            torch_version: 1.8.0
+            cuda_version: 101
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python-version }}
@@ -76,9 +83,18 @@ jobs:
         run: pip install Pillow==6.2.2
       - name: Install PyTorch
         run: pip install torch==${{matrix.torch}} torchvision==${{matrix.torchvision}} -f https://download.pytorch.org/whl/torch_stable.html
+      - name: Install MMCV_CPU
+        if: ${{matrix.torch == '1.3.0+cpu' || matrix.torch == '1.5.0+cpu'}}
+        run: |
+          pip install --use-deprecated=legacy-resolver mmcv-full -f https://download.openmmlab.com/mmcv/dist/cpu/torch${{matrix.torch_version}}/index.html
+          python -c 'import mmcv; print(mmcv.__version__)'
+      - name: Install MMCV_GPU
+        if: ${{matrix.torch == '1.5.0+cu101' || matrix.torch == '1.6.0+cu101' || matrix.torch == '1.7.0+cu101' || matrix.torch == '1.8.0+cu101'}}
+        run: |
+          pip install --use-deprecated=legacy-resolver mmcv-full -f https://download.openmmlab.com/mmcv/dist/cu${{matrix.cuda_version}}/torch${{matrix.torch_version}}/index.html
+          python -c 'import mmcv; print(mmcv.__version__)'
       - name: Install mmseg dependencies
         run: |
-          pip install mmcv-full==latest+torch${{matrix.torch}} -f https://download.openmmlab.com/mmcv/dist/index.html --use-deprecated=legacy-resolver
           pip install -r requirements.txt
       - name: Build and install
         run: rm -rf .eggs && pip install -e .