iOS: Don't search for X11 if building for iOS.  I'm surprised that this hasn't been found until now.  Apparently most devs have the X11 package installed.
iOS: Don't search for X11 if building for iOS.  I'm surprised that this hasn't been found until now.  Apparently most devs have the X11 package installed.

--HG--
branch : v1-7

digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre