clar: fix leaking error reports

We never free error reports when some of the tests have failed or issued
warnings. Plug this memory leak.

clar.c

@@ -612,6 +612,14 @@ clar_test_shutdown(void)
 	}
 
 	for (report = _clar.reports; report; report = report_next) {
+		struct clar_error *error, *error_next;
+
+		for (error = report->errors; error; error = error_next) {
+			free(error->description);
+			error_next = error->next;
+			free(error);
+		}
+
 		report_next = report->next;
 		free(report);
 	}