ci: enforce code style

.github/workflows/build.yml

@@ -9,6 +9,10 @@ jobs:
       - name: install dependencies
         run: |
           sudo apt-get install libboost-dev libboost-program-options-dev
+      - name: check code style
+        run: |
+          make lint
+          [[ $(git status --porcelain | tee >(cat 1>&2) | wc -l) -eq 0 ]]
       - name: build and install
         run: |
           make