It seems GENERIC.X2 and GENERIC.sandpoint were missing. Adding two files let build.sh finish.

cd src/sys/arch/sandpoint/conf
cvs update -r 1.1.94.1 GENERIC.X2
cvs update -r 1.32 GENERIC.sandpoint

with BE 2350 i386 GENERIC.MP machine:
5071.160u 1355.456s 1:02:50.98 170.4% 0+0k 8979+1102706io 10314pf+99w

make release started at:  Sun Oct 21 23:31:35 JST 2007
make release finished at: Mon Oct 22 00:34:21 JST 2007
===> Successful make release
===> build.sh ended:   Mon Oct 22 00:34:21 JST 2007
===> Summary of results:
         build.sh command: ./build.sh -j 4 -m sandpoint release
         build.sh started: Sun Oct 21 23:31:32 JST 2007
         NetBSD version:   4.99.34
         MACHINE:          sandpoint
         MACHINE_ARCH:     powerpc
         Build platform:   NetBSD 4.99.29 i386
         HOST_SH:          /bin/sh
         TOOLDIR path:     /export/src/obj/tooldir.NetBSD-4.99.29-i386
         DESTDIR path:     /export/src/obj/destdir.sandpoint
         RELEASEDIR path:  /export/src/obj/releasedir
         makewrapper:      
	         /export/src/obj/tooldir.NetBSD-4.99.29-i386/bin/nbmake-sandpoint
         Updated /export/src/obj/tooldir.NetBSD-4.99.29-i386/bin/nbmake-sandpoint
         Successful make release
         build.sh ended:   Mon Oct 22 00:34:21 JST 2007
===> .

本当に復活している: