ci(gh-actions): Define "results" job that depends on the result of th…

…e whole matrix

.github/workflows/ci.yml

@@ -54,3 +54,16 @@ jobs:
 
       - name: Build ${{ matrix.package }}
         run: nix build -L --json --no-link '.#${{ matrix.attrPath }}'
+
+  results:
+    if: ${{ always() }}
+    runs-on: ubuntu-latest
+    name: Final Results
+    needs: [build]
+    steps:
+      - run: exit 1
+        if: >-
+          ${{
+               contains(needs.*.result, 'failure')
+            || contains(needs.*.result, 'cancelled')
+          }}