pbulk build problem?

[Bob Nestor <rnestor%mac.com@localhost>]

I've tried to set up a bulk pkgsrc build using pbulk.  The documentation wasn't 
obvious (to me) so I struggled for some time until I got something somewhat 
working.  (Accidentally posted some meaningless crap to the pkgsrc-bulk mailing 
list in the process.) Now I've run into a real head-scratcher.  I must be doing 
something wrong but I'm all out of ideas so I could use a pointer here.

Here's what I've done:

#
# Created the sandbox - this also mounts the filesystems
#
/usr/pkgsrc/mk/bulk/mksandbox /usr/sandbox
#
# Ready to go inside the sandbox to complete the setup
#
chroot /usr/sandbox
########################## Now running inside the sandbox ####################
#
# Create build environment
#
cd /usr/pkgsrc/bootstrap
./bootstrap --prefix=/usr/pbulk --varbase=/usr/pbulk/var  
--workdir=/tmp/pbulk-bootstrap
rm -rf /tmp/pbulk-bootstrap
#
# Added the following to /usr/pbulk/etc/mk.conf
        PACKAGES= /usr/pkgsrc/packages
        WRKOBJDIR= /tmp/pbulk-outer
        PKG_DEVELOPER= yes
        FAILOVER_FETCH= yes
        DISTDIR= /usr/pkgsrc/distfiles
        SKIP_LICENSE_CHECK= yes
        ALLOW_VULNERABLE_PACKAGES= yes
#
# Now build the pbulk tools and install them
#
cd /usr/pkgsrc/pkgtools/pbulk
/usr/pbulk/bin/bmake install
rm -fr /tmp/pbulk-outer
#
# Edited /usr/pkg_bulk/etc/pbulk.conf fixing the following:
        base_url=http://<server>/reports/current/NetBSD-5.1
        master_mode=no
        pkg_rsync_target="<user>@<server>:/public/packages/current/NetBSD-5.1"
        report_rsync_target="<user>@<server>:/public/reports/current/NetBSD-5.1"
        report_recipients=<user>@<server>
        bootstrapkit=
        ignore_missing_dependencies=yes
        skip_age_check=yes
        unprivileged_user=bob
        packages=/usr/pkgsrc/packages
        make=/usr/bin/make
        rsync=:
#
# Ready to do a pbulk build
#
/usr/pbulk/bin/bulkbuild

However, this produces an error "Illegal variable name" in almost every package 
it attempts to build.  I tracked it down to
the MAKE_FLAGS variable used in /usr/pbulk/libexe/pbulk/pkg-build in the 
function run_make().  When I comment this
line out or remove it completely, I can get builds to work.

So can anyone tell me where this variable should be set up and what it needs to 
be set to?  I tried just defining the variable
in both the mk.conf and pbulk.conf files and that didn't help.