This is using ./build.sh.

I'm not seeing any output that I can use for debugging, only:

includes ===> sys/sys
nbmake: don't know how to make properties.h. Stop

nbmake: stopped in /usr/src/sys/sys

*** Failed target:  includes-sys
*** Failed command: _makedirtarget() { dir="$1"; shift; target="$1"; shift; 
case "${dir}" in /*) this="${dir}/"; real="${dir}" ;; .) this="sys/"; real="/usr/src/sys" ;; *) this="sys/${dir}/"; real="/usr/src/sys/${dir}" ;; esac; show=${this:-.}; echo "${target} ===> ${show%/}${1:+ (with: $@)}"; cd "${real}" && /usr/src/obj.i386/tooldir.NetBSD-3.99.19-i386/bin/nbmake _THISDIR_="${this}" "$@" ${target}; }; _makedirtarget sys includes
*** Error code 2

Stop.
nbmake: stopped in /usr/src/sys

-- 
Hisashi T Fujinaka - htodd@twofifty.com
BSEE(6/86) + BSChem(3/95) + BAEnglish(8/95) + MSCS(8/03) + $2.50 = latte