Add "all action stages" job to test-action.yml so nightly can fail.

.github/workflows/test-action.yml

@@ -52,3 +52,24 @@ jobs:
         run: |
           echo "Error! The action should have failed because of the breaking change, but it has not."
           exit 1
+
+  # We need this job so that the overall workflow is considered a success
+  # even if the nightly portions of the test have failed.
+  complete:
+    name: All action stages
+    runs-on: ubuntu-latest
+    needs:
+      - run-tests
+    if: ${{ success() || failure() }}  # Run this job even if a dependency has failed.
+    steps:
+      - name: Job outcomes
+        run: |
+          echo "run-tests: ${{ needs.run-tests.result }}"
+
+      # Fail this required job if any of its dependent jobs have failed.
+      #
+      # Do not attempt to consolidate these steps into one step, it won't work.
+      # Multi-line `if` clauses are not evaluated properly: see the intermediate commits in
+      # https://github.com/obi1kenobi/cargo-semver-checks/pull/405
+      - if: ${{ needs.run-tests.result != 'success' }}
+        run: exit 1