[ARMLinux] Fix the error that armlinux can not compile (#2612)

test=develop

lite/core/mir/subgraph/subgraph_detector.cc

@@ -94,7 +94,7 @@ std::string SubgraphVisualizer::operator()() {
   }
 
   auto res = dot.Build();
-  VLOG(3) << "subgraphs: " << subgraphs_.size() << "\n" << res << std::endl;
+  std::cout << "subgraphs: " << subgraphs_.size() << "\n" << res << std::endl;
   return res;
 }