Use output not env.

Author: desrosj

.github/workflows/check-built-files.yml

@@ -164,7 +164,7 @@ jobs:
           if git diff --quiet; then
             echo "uncommitted_changes=false" >> "$GITHUB_OUTPUT"
           else
-            echo "uncommitted_changes=true" >> "$GITHUB_ENV"
+            echo "uncommitted_changes=true" >> "$GITHUB_OUTPUT"
           fi
 
       - name: Stage changes