I believe this is exactly the procedure which
tools/gcc/README.mknative explains.  If you add a new ${MACHINE_ARCH},
you have to put skeltons under gnu/{lib,usr.bin,usr.sbin}; otherwise
make fails with "no such file or directory".  This script doesn't take
account into this skelton thing.

http://www.netbsd.org/~uebayasi/build-sh-mknative.patch

Masao