midori: fix build with dirty vala

* there is only one line added to default waf file
  in unpack_wafdir() just before last chdir and return
  because those files are downloaded and cannot be patched in normal way
  os.system("sed -i \"s/version=output.split/version=output.replace('-dirty','').split/g\" wafadmin/Tools/vala.py")

* It fails to parse version like this
  /OE/shr-core/tmp/sysroots/x86_64-linux/usr/bin/valac --version
  Vala 0.12.1-dirty
  reporting 0.0.0 instead which breaks configure

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