Fail CI if workflow needs regenerating.

.github/workflows/pull-request.yml

@@ -20,11 +20,13 @@ jobs:
           python3 -m pip install --upgrade pip virtualenv
           sudo apt update
           python3 ./mach bootstrap
-      - name: Tidy
-        run: python3 ./mach test-tidy --no-progress --all
+      - name: Workflow check
+        run: ./etc/ci/workflow_changed.sh
       - name: Release build
         run: python3 ./mach build --release
       - name: Unit tests
         run: python3 ./mach test-unit --release
+      - name: Tidy
+        run: python3 ./mach test-tidy --no-progress --all
       - name: Lockfile check
         run: ./etc/ci/lockfile_changed.sh