fix: fix if condition

Author: suzuki-shunsuke

.github/workflows/test.yml

@@ -28,7 +28,8 @@ jobs:
   build:
     runs-on: ubuntu-latest
     needs: setup
-    if: false
+    # if services is empty, the build job is skipped
+    if: "join(fromJSON(needs.setup.outputs.services), '') != ''"
     strategy:
       matrix:
         service: ${{fromJSON(needs.setup.outputs.services)}}