how to get the LOCALBASE in pkg_add?

[Keivan Motavalli <keivan%motavalli.me@localhost>]

Hi, pkgsrc allows the user to set a LOCALBASE (defaulting to /usr/pkg) in 
mk.conf.

I'm trying to understand pkgtools/pkg_install and it seems that no LOCALBASE 
can be set in pkg_install.conf, as it's not parsed by pkgtools/pkg_install/
files/lib/parse-config.c;

only PKG_DBDIR is set there, defaulting to /var/db/pkg (pkgtools/pkg_install/
lib/pkgdb.c).

I need to create a directory for a new feature that, if not disabled by the 
user, I'd like to be under LOCALBASE/pkgetc (and not under /var/db/pkgetc, in 
order to support unprivileged installations). 

Is there any way to get which is the LOCALBASE in pkg_install, without 
resorting to parsing mk.conf?