I compiled a NetBSD-1.6.1 kernel, but had to compile and install the new
config program.

I would like to build a 1.6.1 world but don't want to install over /
until later.  I think I have to use -D to do so.

Thus I am trying to build a 1.6.1 world in /mnt/tmp using this command:
./build.sh -u -D /mnt/tmp

I am getting a bomb-out as follows:
...
/usr/src/tools/obj/tools.NetBSD-1.5.2-i386/bin/i386--netbsdelf-gcc -O2  -Wall -W
strict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-uninitialized  -Werr
or  -I/usr/src/gnu/libexec/uucp/cu/../common_sources -DVERSION=\"1.06.1\" -DPOSI
X_HEADERS -nostdinc -isystem /mnt/tmp/usr/include  -c /usr/src/gnu/libexec/uucp/
cu/../common_sources/copy.c
/usr/src/tools/obj/tools.NetBSD-1.5.2-i386/bin/i386--netbsdelf-gcc   -o cu -nost
dlib  /mnt/tmp/usr/lib/crt0.o /mnt/tmp/usr/lib/crtbegin.o cu.o prot.o log.o chat
.o conn.o copy.o /usr/src/gnu/libexec/uucp/libunix/obj/libunix.a /usr/src/gnu/li
bexec/uucp/libuuconf/obj/libuuconf.a /usr/src/gnu/libexec/uucp/libuucp/obj/libuu
cp.a -L/mnt/tmp/usr/lib  -lgcc -lc -lgcc /mnt/tmp/usr/lib/crtend.o
/mnt/tmp/usr/lib/crt0.o: In function `___start':
/mnt/tmp/usr/lib/crt0.o(.text+0x9c): undefined reference to `atexit'
/mnt/tmp/usr/lib/crt0.o(.text+0xbe): undefined reference to `exit'
/mnt/tmp/usr/lib/crt0.o: In function `_rtld_setup':
/mnt/tmp/usr/lib/crt0.o(.text+0x122): undefined reference to `__syscall'
/mnt/tmp/usr/lib/crt0.o(.text+0x133): undefined reference to `__syscall'
/mnt/tmp/usr/lib/crt0.o(.text+0x155): undefined reference to `__syscall'
/mnt/tmp/usr/lib/crt0.o(.text+0x166): undefined reference to `__syscall'
/mnt/tmp/usr/lib/crt0.o(.text+0x177): undefined reference to `atexit'
cu.o: In function `main':
cu.o(.text+0xf0): undefined reference to `_ctype_'
cu.o(.text+0x112): undefined reference to `zbufalc'
...[lots more commonly-named functions]...

What am I doing wrong?