Building a cross compiler for x86_64

["Frank W. Miller" <fwmiller@xxxxxxxxxxx>]

I've determined that my gcc build does not support the -w64 compile
option.  (I'm running FC8 and its not compiled in by default apparently)

So, I need to build a cross compiler.  I have binutils-2.18 and
gcc-4.2.3 and I'm ready to do a build.  First question is, what platform
should I target, i.e. what should --target=??? be for both binutils and
gcc?

Thanks,
FM