[Bug libffi/47164] New: libffi fails to build for alternate target in multilib configuration

[vityan at vityan dot sytes.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47164

           Summary: libffi fails to build for alternate target in multilib
                    configuration
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libffi
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: vit...@vityan.sytes.net
              Host: i686-w64-mingw32
            Target: i686-w64-mingw32,x86_64-w64-mingw32
             Build: i686-pc-mingw32(msys)


Created attachment 22894
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22894
libffi multilib support fix for MingW64

Then multilib is enabled for toolchain(--enable-multilib) libffi fails to build
for alternative(secondary) target.
The issue caused by libffi's configury system only handling the main
host/target without any respect to multilib.

For x86_64-w64-mingw32 i've forced to manually import files from libffi
3.0.10-cvs into libffi/src/x86/ from GCC tree but this is out of scope of
current issue.

This issue is global for many targets.
I've made a patch fixing this issue for i686-*-mingw32,x86_64-*-mingw32 targets
with multilib configuration.