Cancel previous CI workflow runs

(cherry picked from commit a249373bf5)

# Conflicts:
#	README.md

.github/workflows/build_check.yml

@@ -20,6 +20,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - name: Cancel previous runs
+        uses: styfle/cancel-workflow-action@0.5.0
+        with:
+          access_token: ${{ github.token }}
+
       - name: Clone repo
         uses: actions/checkout@v2