ci: label formality failures

Add or remove 'not following guidelines' label based on formality check
status.

Signed-off-by: George Sapkin <george@sapk.in>

.github/workflows/multi-arch-test-build.yml

@@ -8,6 +8,31 @@ jobs:
     name: Test Formalities
     uses: openwrt/actions-shared-workflows/.github/workflows/formal.yml@main
 
+  label_formality_status:
+    name: Add formality check labels
+    runs-on: ubuntu-slim
+    needs: formalities
+    if: always()
+    permissions:
+      pull-requests: write
+
+    steps:
+      - name: Add 'not following guidelines' label
+        if: needs.formalities.result == 'failure'
+        uses: buildsville/add-remove-label@v2.0.1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          labels: "not following guidelines"
+          type: add
+
+      - name: Remove 'not following guidelines' label
+        if: needs.formalities.result == 'success'
+        uses: buildsville/add-remove-label@v2.0.1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          labels: "not following guidelines"
+          type: remove
+
   build:
     name: Feeds Package Test Build
     needs: formalities