Add missing scikit-build install

.github/workflows/test.yaml

@@ -21,7 +21,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip pytest cmake
+          python -m pip install --upgrade pip pytest cmake scikit-build
           python3 setup.py develop
       - name: Test with pytest
         run: |