Building ports in jails after staging support

[Frank Volf]

Hi,

I'm having a FreeBSD 9.1-RELEASE system with some jails.
The jails have problems building/upgrading ports after staging support 
was added to the /usr/ports tree.
I'm using portupgrade for the upgrades (but that is not political, if 
another tool does the job then that is fine as well).

  I searched the archives of this list and if I understood that there 
are two problem areas:
1) All jails share a union-mounted read-only copy of the /usr/ports 
tree, and staging tries by default to write in /usr/ports
2) My jails are build according to the description in the FreeBSD 
handbook and the symbolic link in the jails that points usr/local to 
../s/usr-local is causing problems as well.

I found several messages from people describing work-arounds (e.g. 
setting PACKAGES or NO_STAGE in /etc/make.conf), adjusting PREFIX in 
pkgtools.conf.
Some messages seem to be contradicting each other (like NO_STAGE should 
not be defined), and some solution only solve one of the two problems.

So, my question is simply: is there an official (future proof) way how 
to fix this? In other words, what should I do to get portupgrade or any 
other port mgmt tool working again in the jails with my setup?

Regards,

Frank