I think this might be useful for people, that use custom build flags when building NetBSD. It is loosely based on ftp://ftp.pulsar-zone.net/building-netbsd.txt
Sometimes builds fail because things doesn't fit in 2.88M when built with certain optimizations. So if it's your case, then do:
# ./build.sh build distribution sets
# ./build.sh release
you'll in have your sets in your RELEASEDIR (/usr/obj/releasedir).
Do this for each kernel you want to build install set for
# ./build.sh kernel=GENERIC releasekernel=GENERIC
Then you may install over network, or build install floppies/cdrom without optimization.