Attempt to fix the mingw32 bot.

This should hopefully fix
http://lab.llvm.org:8011/builders/clang-x86_64-darwin11-self-mingw32

Merged from r182446
Author: Rafael Espindola <rafael.espindola@gmail.com>
Date:   Wed May 22 02:30:47 2013 +0000

llvm-svn: 190579