This build is needed before the newer gtk2 can build, and many builds depend on
the newer gtk2.  I tried looking at this a bit, but I'm not sure where to begin
to debug it.  It seems it's failing in a testcase that is run during the build
with:

libtool: link: gcc -pthread -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include
-pthread -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include
-fno-strict-aliasing -Wsign-compare -Wcast-align -Wpointer-arith
-Wnested-externs -Wmissing-prototypes -Wmissing-declarations -Wchar-subscripts
-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
--param=ssp-buffer-size=4 -m32 -o .libs/barapp barapp.o -pthread -pthread
-Wl,--export-dynamic  ../../girepository/.libs/libgirepository-1.0.so -lffi
-ldl -lgio-2.0 -lgobject-2.0 -lgmodule-2.0 -lgthread-2.0 -lrt -lglib-2.0
-pthread
env LPATH=.libs  env PYTHONPATH=../..:../..:YTHONPATH
UNINSTALLED_INTROSPECTION_SRCDIR=../.. UNINSTALLED_INTROSPECTION_BUILDDIR=../..
../../tools/g-ir-scanner -v --add-include-path=../../gir --add-include-path=.
-v --add-include-path=../../gir --add-include-path=. --namespace=BarApp
--nsversion=1.0 --libtool="/bin/sh ../../libtool" --program=./barapp 
--pkg=gobject-2.0 --include=GObject-2.0 --strip-prefix=Bar  ./barapp.c
./barapp.h --output BarApp-1.0.gir
../../tools/g-ir-compiler --includedir=. --includedir=../../gir
--includedir=../../gir --includedir=. BarApp-1.0.gir -o BarApp-1.0.typelib
../../tools/g-ir-generate --includedir=. --includedir=../../gir
annotation-1.0.typelib -o annotation-1.0.tgir
../../tools/g-ir-generate --includedir=. --includedir=../../gir
drawable-1.0.typelib -o drawable-1.0.tgir
../../tools/g-ir-generate --includedir=. --includedir=../../gir foo-1.0.typelib
-o foo-1.0.tgir
**
ERROR:ginfo.c:337:g_base_info_get_name: code should not be reached
make[3]: Leaving directory
`/builddir/build/BUILD/gobject-introspection-0.6.7/tests/scanner'
make[3]: *** [foo-1.0.tgir] Aborted
make[3]: *** Deleting file `foo-1.0.tgir'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory
`/builddir/build/BUILD/gobject-introspection-0.6.7/tests'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/builddir/build/BUILD/gobject-introspection-0.6.7'
make: *** [all] Error 2


Looking at ginfo.c, it seems to call an assert if g_base_info_get_name is
passed a GBaseInfo pointer that matches G_INFO_TYPE_TYPE, or doesn't match any
of the other G_INFO types in info->type.  Where exactly that is getting set in
the failing testcase is beyond me.  

You can find the full build logs here:

http://ppc.koji.fedoraproject.org/koji/taskinfo?taskID=46095

And the build files from that buildroot are here:

http://jwboyer.fedorapeople.org/pub/gobject-introspection-0.6.7-build.tar.gz