midori: force host-python dependency for waf build-system

Fixes http://autobuild.buildroot.net/results/d48/d48b68dd6a43fa9a224237e8f458ca8987a3d7b4/



Similar to the recent fix to jack2 (fc8fcec3). The waf version included
in midori (1.5.19) is not compatible with python 3.4.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>