Hack child_process.fork to use execute script with atom-shell.

lib/child_process.js

@@ -49,6 +49,18 @@ exports.fork = function(modulePath /*, args, options*/) {
   options.stdio = options.silent ? ['pipe', 'pipe', 'pipe', 'ipc'] :
       [0, 1, 2, 'ipc'];
 
+  // When forking a child script, we setup a special environment to make
+  // the atom-shell binary run like the upstream node.
+  if (!options.env) {
+    options.env = Object.create(process.env);
+  }
+  options.env['ATOM_SHELL_INTERNAL_RUN_AS_NODE'] = 1;
+
+  // On Mac we use the helper app as node binary.
+  if (!options.execPath && process.type && process.platform == 'darwin') {
+    options.execPath = process.helperExecPath;
+  }
+
   options.execPath = options.execPath || process.execPath;
 
   return spawn(options.execPath, args, options);