[llvm][lit] fix writing results to file

Author: da-viper

llvm/utils/lit/lit/reports.py

@@ -286,7 +286,8 @@ def _write_results_to_file(self, tests, elapsed, file):
 
         json_data = {"traceEvents": events}
 
-        json.dump(json_data, time_trace_file, indent=2, sort_keys=True)
+        with open(self.output_file, "w") as time_trace_file:
+            json.dump(json_data, time_trace_file, indent=2, sort_keys=True)
 
     def _get_test_event(self, test, first_start_time):
         test_name = test.getFullName()