src/Makefile.inc1 rev. 1.590, it can allow installing a world
cross-built for a different arch over the live system. The procedure
is more or less as follows:
cp -R /rescue /rescue.old
make installkernel TARGET_ARCH=foo
make -DNO_RTLD installworld TARGET_ARCH=foo
^^^^^^^^^
PATH=/rescue.old
chflags noschg /libexec/ld-elf.so.1
cp /usr/obj/foo/usr/src/libexec/rtld/ld-elf.so.1 /libexec
chflags schg /libexec/ld-elf.so.1
<ditto for ld-elf32.so.1 if installing for amd64>
reboot