Sparc64 support

[Adrian Chadd]

Hi,

I've tested it with mips/mips64. It works out mostly okay. There are
still rough edges, because in the mips world we have different
defaults in our base system gcc to what the current toolchain expects.
But at least for mips/mips64 it spits out a kernel and binaries that
work.

What I did to make the MIPS bits call the external toolchain:

make <existing options> NO_WERROR=1 CROSS_TOOLCHAIN=mips-gcc buildworld

.. so in theory the sparc64 stuff may just be:

pkg install sparc64-gcc sparc64-xtoolchain-gcc
make <existing stuff> NO_WERROR=1 CROSS_TOOLCHAIN=sparc64-gcc buildworld


-adrian