run benchmark if there is benchmark label or on main branch

Signed-off-by: Thing-han, Lim <[email protected]>

.github/workflows/bench.yml

@@ -9,7 +9,7 @@ on:
 jobs:
   bench:
     runs-on: self-hosted-rpi4
-    if: github.repository_owner == 'pq-code-package'
+    if: github.repository_owner == 'pq-code-package' && (github.event.pull_request.labels == "benchmark" || github.ref == "refs/heads/main")
     steps:
       - uses: actions/checkout@v4
       - name: Setup nix