midori: disable gtk3

* waf configure/waf build always hangs when gtk3 was built before midori

* usually it's on this line:
  | Checking for program glib-genmarshal        : /OE/shr-core/tmp-eglibc/sysroots/x86_64-linux/usr/bin/glib-genmarshal
  | Checking for program glib-mkenums           : /OE/shr-core/tmp-eglibc/sysroots/x86_64-linux/usr/bin/glib-mkenums
  | Checking for program msgfmt                 : /OE/shr-core/tmp-eglibc/sysroots/x86_64-linux/usr/bin/msgfmt
  | Checking for program intltool-merge         : /OE/shr-core/tmp-eglibc/sysroots/x86_64-linux/usr/bin/intltool-merge
  | Checking for header locale.h                :
  but I guess, that's it's because glib-genmarshal or glib-mkenums,
  because if I finish do_configure somehow manually then waf build hangs
  as soon as it starts glib_genmarshal (or seemingly a bit later if there is more processes)
  | Waf: Entering directory `/OE/shr-core/tmp-eglibc/work/armv7a-vfp-neon-oe-linux-gnueabi/midori/midori-0.4.3-r0/midori-0.4.3/_build_'
  | [  1/121] glib_genmarshal: midori/marshal.list -> _build_/default/midori/marshal.h _build_/default/midori/marshal.c
  | [  2/121] valac: katze/midori-uri.vala midori/midori-extensions-column.vala -> _build_/default/katze/midori-uri.c _build_/default/midori/midori-core.h _build_/default/midori/midori-core.vapi _build_/default/midori/midori-core.deps _build_/default/midori/midori-extensions-column.c _build_/default/midori/midori-core.h _build_/default/midori/midori-core.vapi _build_/default/midori/midori-core.deps
  | ../katze/midori-uri.vala:19.60-19.74: warning: use of possibly unassigned parameter `path'
  | ../katze/midori-uri.vala:19.60-19.74: warning: use of possibly unassigned parameter `path'
  | ../katze/midori-uri.vala:19.60-19.74: warning: use of possibly unassigned parameter `path'
  | ../katze/midori-uri.vala:134.34-134.49: warning: use of possibly unassigned parameter `label'
  | ../katze/midori-uri.vala:134.13-134.31: warning: use of possibly unassigned parameter `checksum'
  | Waf: Leaving directory `/OE/shr-core/tmp-eglibc/work/armv7a-vfp-neon-oe-linux-gnueabi/midori/midori-0.4.3-r0/midori-0.4.3/_build_'
  | Build failed:  -> task failed (err #-15):
  |       {task: glib_genmarshal marshal.list -> marshal.h,marshal.c}

* I was able to reproduce this 100%, I know that before it also hanged from
  time to time in waf

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>