Skip ecosystem check when no changes detected (#8520)

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## Summary

For example, https://github.com/astral-sh/ruff/pull/8512 doesn't need
ecosystem check
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.github/workflows/ci.yaml

@@ -184,7 +184,11 @@ jobs:
       - cargo-test-linux
       - determine_changes
     # Only runs on pull requests, since that is the only we way we can find the base version for comparison.
-    if: github.event_name == 'pull_request'
+    # Ecosystem check needs linter and/or formatter changes.
+    if: github.event_name == 'pull_request' && ${{
+      needs.determine_changes.outputs.linter == 'true' ||
+      needs.determine_changes.outputs.formatter == 'true'
+      }}
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v4