iOS: Guard a media dir variable update since we want to preserve the relative paths on iOS
iOS: Guard a media dir variable update since we want to preserve the relative paths on iOS

--HG--
branch : v1-7

bhlzlx/ogre,bhlzlx/ogre,ehsan/ogre,bhlzlx/ogre,ehsan/ogre,ehsan/ogre,bhlzlx/ogre,ruleless/ogre,ruleless/ogre,bhlzlx/ogre,ruleless/ogre,ruleless/ogre,ruleless/ogre,ehsan/ogre,ehsan/ogre,ruleless/ogre,bhlzlx/ogre