PKG_NG: pkg deinstall fails with "argument list too long"

[Stefan Esser]

PKG_NG seems to have introduced a limit on the size of ports that can be
deinstalled:

# cd /usr/ports/math/lapack
#  make deinstall
===>  Deinstalling for math/lapack
===>   Deinstalling lapack-3.4.0_2
The following packages will be deinstalled:

        lapack-3.4.0_2

The deinstallation will free 28 MB
Deinstalling lapack-3.4.0_2...lapack-3.4.0_2 is required by:
qrupdate-1.1.1, deleting anyway
pkg: Cannot run script(DEINSTALL): Argument list too long
*** [deinstall] Error code 3

This is on an up-to-date -CURRENT with freshly fetched ports and
pkg-1.0.r6_1 and WITH_PKGNG=yes in /etc/make.conf.

Regards, STefan