benchmark: use node v4 syntax in common.js

Using new syntax such as `...args` means that the benchmark suite can't
be used with older node versions. This changes the `...args` syntax to a
good old `Array.prototype.slice`.

Refs: #8932 (comment)
PR-URL: #9064
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

benchmark/common.js

@@ -208,11 +208,14 @@ Benchmark.prototype.report = function(rate, elapsed) {
   });
 };
 
-exports.v8ForceOptimization = function(method, ...args) {
+exports.v8ForceOptimization = function(method) {
   if (typeof method !== 'function')
     return;
+
   const v8 = require('v8');
   v8.setFlagsFromString('--allow_natives_syntax');
+
+  const args = Array.prototype.slice.call(arguments, 1);
   method.apply(null, args);
   eval('%OptimizeFunctionOnNextCall(method)');
   method.apply(null, args);