flambda-backend: Add gc-timings to collect timing information from the GC (ocaml-flambda#1089)

Author: poechsel

runtime/eventlog.c

@@ -115,8 +115,8 @@ static int64_t time_counter(void)
   return
     (int64_t)t.tv_sec  * (int64_t)1000000000 +
     (int64_t)t.tv_nsec;
-
-
+#else
+  return 0;
 #endif
 }