On Mac OS X 10.6.4, config.guess is returning "x86_64-apple-darwin10.4.0". Which is correct; 
however, clone/bootstrap/set_soenv.in only supports m/^i[3456]86/ & m/^powerpc/.
I just copied the i386 block into my new x86_64 block for now:
{
          print "Setting values for Mac OS X/Darwin on x86... ";
          $outfile        = "MacOSXX86Env.Set"; 
          $CPU            = "I";
          $CPUNAME        = "INTEL";
          $OUTPATH        = "unxmacxi";
}
I believe that we might need to change it to something like the following if we ever want to 
support a 64bit build on Mac:
{
          print "Setting values for Mac OS X/Darwin on x86... ";
          $outfile        = "MacOSXX86_64Env.Set"; 
          $CPU            = "X";
          $CPUNAME        = "X86_64";
          $OUTPATH        = "unxmacxx";
}
However, I don't think the rest of the build system would handle that very well.
Joe P.
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