`child_process.spawnSync()` throws an error when `options` argument is shared

Calling `child_process.spawnSync()` 3 times with shared `options` argument throws an error.

`test.js`:

``` javascript
var spawn = require('child_process').spawnSync;

var ls;
var opts = {
  stdio: 'inherit'
};

ls = spawn('ls', [], opts);
ls = spawn('ls', [], opts);
ls = spawn('ls', [], opts);
```

This bug has been fixed on io.js v1.1.0.

See also: iojs/io.js#576, iojs/io.js#579
