libffi is broken for x32

[H.J. Lu]

This libffi commit:

13e2d7b92557a9511a0414df82bf2df3edc55cba is the first bad commit
commit 13e2d7b92557a9511a0414df82bf2df3edc55cba
Author: Anthony Green <gr...@moxielogic.com>
Date:   Thu Jan 10 10:52:02 2013 -0500

    Handle both 32 and 64-bit x86 builds regardless of target triple

breaks x32.

-- 
H.J.