The problem is when I try to install the userland.

   mount build_machine:/usr/export /mnt
   cd /mnt/src
   su
   sh build.sh -x -X ../xsrc -O ../builds/i386/obj -T ../builds/i386/tools -U 
  install=/
  ===> build.sh command: 
  build.sh -x -X ../xsrc -O ../builds/i386/obj -T ../builds/i386/tools -U 
  install=/
  ===> build.sh started: Mon Mar 19 13:18:35 CET 2007
  ===> MACHINE:          i386
  ===> MACHINE_ARCH:     i386
  ===> TOOLDIR path:     /mnt/src/../builds/i386/tools
  ===> DESTDIR path:     /mnt/src/../builds/i386/obj/destdir.i386
  ===> RELEASEDIR path:  /mnt/src/../builds/i386/obj/releasedir
  rm: /mnt/src/../builds/i386/tools/bin/nbmake-i386: Permission denied
  eval: cannot create /mnt/src/../builds/i386/tools/bin/nbmake-i386: permission 
  denied

I have found that build.sh really expects the source tree and the obj
to be at the same paths.  It may be that the actual rules are less
strict, but I don't run it via NFS, and I don't move things around (or
if I do I rm -rf /usr/obj and start over).

The scripts I pointed you to install from release sets, so they avoid
all of this.  And they don't require NFS, which is too scary to run in
many environments (from a security viewpoint).