rubinius/rubinius — pull request #1737 by ryoqun (2012-05-20 10:32:35+00:00)
Title: Fix libffi build issue with Clang

This cherry-picks a commit by hand to fix a libffi build failure with clang.
In particular, I applied the following patch from the official libffi
repository:
https://github.com/atgreen/libffi/blob/master/patches/x86_pcrel_test

References:
http://bugs.python.org/issue12812
https://bugzilla.mozilla.org/show_bug.cgi?id=631928
http://sourceware.org/ml/libffi-discuss/2011/msg00024.html

Because I'm changing any part of the build system, I'm being careful :)

Could anybody test building with this patch?

I tested on Ubuntu 12.04 (GCC 4.6 and Clnag 3.0)