Add success job

.github/workflows/rust.yml

@@ -39,3 +39,15 @@ jobs:
       run: cargo doc --verbose --no-deps
     - name: Check big endian
       run: cargo check --target powerpc64-unknown-linux-gnu --verbose --all
+  success:
+    needs:
+      - build
+    runs-on: ubuntu-latest
+    # GitHub branch protection is exceedingly silly and treats "jobs skipped because a dependency
+    # failed" as success. So we have to do some contortions to ensure the job fails if any of its
+    # dependencies fails.
+    if: always() # make sure this is never "skipped"
+    steps:
+      # Manually check the status of all dependencies. `if: failure()` does not work.
+      - name: check if any dependency failed
+        run: jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}'