The problem seems to be an odd placement of glibconfig.h header:
A make in packages/gtk results in:

/bin/sed -e "1s,@AWK\@,/usr/bin/gawk," < mk_enums.awk > mk_enums
chmod +x mk_enums
/bin/sed -e "1s,@AWK\@,/usr/bin/gawk," < cpp.awk > cpp
chmod +x cpp
gawk \

         -vPKG_CONFIG='/usr/bin/pkg-config' \
         -v_prefixes='g atk pango' \
         -v_libs="gobject-2.0 gdk-2.0 gdk-pixbuf-2.0 pango gtk+-2.0 atk" \
         -v_files="glib-object.h gdk/gdk.h gdk-pixbuf/gdk-pixbuf.h gtk/gtk.h atk/atk.h pango/pango.h ./placer.h" -f

         | while read i; do \
           case "$i" in \
             error:*) \
               echo "$i" >&2; exit 1;; \
             */gobject/*) \
               echo "$i" ;; \
             */glib/*) \
               case " glib/goption.h glib/gdate.h " in \
                 *" glib/`basename $i` "*) echo "$i" ;; \
                 *) ;; \
               esac ;; \
             *) \
               echo "$i" ;; \
           esac; \
         done > order

Checking where this header is shows:

tkack@tkackxp3:~/Sources/Smalltalk/GNU/VM/smalltalk/packages/gtk$ pkg-config --cflags glib-2.0
-I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include

For some odd reason is the glibconfig.h header in /usr/lib/glib-2.0/include.

Workaround:

sudo ln -s /usr/lib/glib-2.0/include/glibconfig.h /usr/include/glib-2.0/

I have not pinned down the problem in mkorder.awk yet.

$ pkg-config --cflags glib-2.0
-I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include  
$ ls -l /usr/lib64/glib-2.0/include 
total 8
-rw-r--r-- 1 root root 6568 2009-06-27 08:12 glibconfig.h

diff --git a/packages/gtk/mkorder.awk b/packages/gtk/mkorder.awk
index fd65832..402318c 100644
--- a/packages/gtk/mkorder.awk
+++ b/packages/gtk/mkorder.awk
@@ -45,7 +45,7 @@ BEGIN {
 function process_lib(lib, prog, i) {
     prog = PKG_CONFIG " --cflags " lib
     while (prog | getline)
-        for (i = 1; i < NF; i++)
+        for (i = 1; i <= NF; i++)
             if ($i ~ /^-I/)
                 paths[++n_paths] = substr($i, 3)
     close(prog)