Fix compilation error on Linux.
Fix compilation error on Linux.

dustinblackman/node-runas,atom/node-runas,atom/node-runas,dbkaplun/node-runas,dustinblackman/node-runas,pombredanne/node-runas,pombredanne/node-runas,paulcbetts/node-runas,dbkaplun/node-runas,paulcbetts/node-runas