Update the path to iossim in the script run by Xcode to launch tests on simulator.

BUG=228157

Review URL: https://chromiumcodereview.appspot.com/14373011

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@197491 4ff67af0-8c30-449e-8e8b-ad334ec8d88c