ci: delay error to patch upload

Author: JohelEGP

.github/workflows/regression-tests.yml

@@ -50,3 +50,10 @@ jobs:
         name: ${{ matrix.compiler }}-patch.diff
         path: regression-tests/${{ matrix.compiler }}-patch.diff
         if-no-files-found: ignore
+
+    - name: Guidance on failure
+      run: |
+        if [[ -f "${{ matrix.compiler }}-patch.diff" ]]; then
+          echo "There were failing tests; apply the uploaded patches or check the step 'Run regression tests'."
+          exit 1
+        fi