src: improve startup time

Previously, V8:SetFlagsFromCommandLine was being called even if v8_argc
was 0. This change prevents that from being called unless v8 arguments
are actually passed.

Improves startup time by about 5%.

PR-URL: https://github.com/nodejs/node/pull/2483
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

src/node.cc

@@ -3706,6 +3706,7 @@ void Init(int* argc,
 #endif
   // The const_cast doesn't violate conceptual const-ness.  V8 doesn't modify
   // the argv array or the elements it points to.
+  if (v8_argc != 0)
     V8::SetFlagsFromCommandLine(&v8_argc, const_cast<char**>(v8_argv), true);
 
   // Anything that's still in v8_argv is not a V8 or a node option.