recommended setup for building ports in development env?

[Gary Aitken]

May be better to ask this on ports but thought I would check here first.

I'm trying to set up a development environment for a few ports.
I established a parallel ports tree and set the environment variables
   PREFIX=${MYFREEBSD}/usr/local
   WORKDIR=${MYFREEBSD}/var/db/portsnap
   PORTSDIR=${MYFREEBSD}/usr/ports

With those set, I can build and install some things.

For example, I can build and install graphics/ufraw, and with my PATH
properly extended to include ${MYFREEBSD}/usr/local/bin I can execute it.
I can also build and install x11/babl into ${MYFREEBSD}.
Running a normally built gimp finds the new libbabl located in a
different, non-standard place:
   $ ldd `which gimp` | grep babl
         libbabl-0.1.so.0 => /usr/home/.../usr/local/lib/libbabl-0.1.so.0
I didn't expect that to work; nice.

However, when I go to build graphics/gegl it fails because it can't find
the installed babl:
   ===>   gegl-0.3.34 depends on shared library: libbabl-0.1.so - not found

If I set
   LOCALBASE=${MYFREEBSD}/usr/local
it wants to rebuild all dependencies, since it doesn't find any of the
normally installed stuff.

Adding
    -L${MYFREEBSD}/usr/local/lib      to LDFLAGS
   -I${MYFREEBSD}/usr/local/include  to CPPFLAGS
in the Makefile doesn't solve the problem.

Is there a good solution to this, or do I have to set LOCALBASE with the
resulting build of everything else, not just the things that I need to
upgrade for this work?  Hopefully there's a way to extend the normal
search path for port builds?

Thanks for any hints,

Gary