> Hmm, works fine here on -current and in a 4.0 chroot on -current:

> $ mount | grep /usr/src
> /a/src/nbsd/4 on /usr/src type null (read-only, nosuid, nodev, local)
> $ cd /usr/src
> $ ./build.sh -U -O ~/temp/obj -t ~/temp/obj/tools tools
> ===> build.sh command: ./build.sh -U -O /home/build/temp/obj -T /home/build/temp/obj/tools tools
> ===> build.sh started: Sat Nov 10 13:09:17 UTC 2007
> ===> NetBSD version:   4.0_RC4
> ===> MACHINE:          i386
> ===> MACHINE_ARCH:     i386
> ===> Build platform:   NetBSD 4.0_RC4 i386
> ===> HOST_SH:          /bin/sh
> ===> No /home/build/temp/obj/tools/bin/nbmake, needs building.
> ===> Bootstrapping nbmake
> [...]
> rm -f PREVIOUSTOOLDIR
> echo /home/build/temp/obj/tools >PREVIOUSTOOLDIR
> dependall ===> host-mkdep
> rm -f host-mkdep
> [...]

Ok. I don't know what I did, but now
    ./build.sh -O /srv/obj -u tools
works fine.

But now I have 
0 src>./build.sh -O /srv/obj -T /srv/obj/tools kernel=GENERIC 
===> build.sh command: ./build.sh -O /srv/obj -T /srv/obj/tools kernel=GENERIC
===> build.sh started: Sun Nov 11 12:09:43 EET 2007
===> NetBSD version:   4.0_RC4
===> MACHINE:          i386
===> MACHINE_ARCH:     i386
===> Build platform:   NetBSD 4.0_RC3 i386
===> HOST_SH:          /bin/sh
===> TOOLDIR path:     /srv/obj/tools
===> DESTDIR path:     /srv/obj/destdir
===> RELEASEDIR path:  /srv/obj/release
===> makewrapper:      /srv/obj/tools/bin/nbmake-i386
===> Updated /srv/obj/tools/bin/nbmake-i386
===> Building kernel without building new tools
===> Building kernel:  GENERIC
===> Build directory:  /srv/src/sys/arch/i386/compile/GENERIC
mkdir: /srv/src/sys/arch/i386/compile/GENERIC: Read-only file system

ERROR: Cannot mkdir: /srv/src/sys/arch/i386/compile/GENERIC
*** BUILD ABORTED ***
1 src>

/etc/mk.conf:
   MAKEOBJDIR=/srv/obj
   TOOLDIR=/srv/obj/tools
   DESTDIR=/srv/obj/destdir
   RELEASEDIR=/srv/obj/release

P.S.
I whould prefer to use MAKEOBJDIR=/srv/obj in mk.conf
instead of ./build.sh -O but this doesn't work :-( Is this bug-o-feature?

-- 
Best regards, Aleksey Cheusov.