Temporarily disable test that fails on Mac OS X 10.9.

PR18322. This test will be reenabled when the SDK gets fixed. In the meantime,
it is pretty disruptive to have this test keep failing.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200256 91177308-0d34-0410-b5e6-96231b3b80d8