Since the website has changed from codesourcery to sourcery.mentor, the downalod of the ext toolchain fails.
Thanks for the heads up, committed the patch. Normally buildroot should still work when upstream URLs change as we have a backup mirror (http://sources.buildroot.net), but mentor.com unfortunately redirects the old tarball URLs to their new front page instead of generating a 404. I have mailed the mentor webmaster to get them to fix this, but chances are that they won't do it.