[Gimp-developer] GIMP looking for babl and GEGL outside the prefix

[Elle Stone <ellestone ninedegreesbelow com>]

I installed babl/GEGL/GIMP from git in a prefix. Then I installed 
babl/GEGL/GIMP-2.8 from Gentoo portage. When I tried to update GIMP from 
git in the prefix, I got the following terminal output

core/libappcore.a(gimphistogram.o): In function `gimp_histogram_calculate':
/home/elle/code/gimpdefault/build/gimp/app/core/gimphistogram.c:261: 
undefined reference to `babl_format_get_model'
. . .
collect2: error: ld returned 1 exit status
Makefile:890: recipe for target 'gimp-2.9' failed
make[4]: *** [gimp-2.9] Error 1
. . .

This problem is documented here:
http://wiki.gimp.org/wiki/Hacking:Problems_and_solutions#GIMP_build_fails_for_missing_BABL_function

Why is GIMP looking for babl outside the prefix?

Is there a way to make GIMP look inside the prefix and ignore the babl 
install that's outside the prefix? I mean besides uninstalling babl/GEGL 
from portage before updating GIMP in the prefix?

Elle