node-gyp: download header tarball for compile

Temporary fix only, node-gyp needs to be aware of whether it can even
download this file for the current runtime so that information needs to
come from the process itself.

Floating patch on npm.

PR-URL: https://github.com/nodejs/io.js/pull/2066


Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Ryan Graham <ryan@strongloop.com>