Qt Creator does not use correct mkspec (on Mac OSX)

Qt Creator incorrectly assumes that the mkspec is macx-g++ (when building for iOS on Mac OSX), not the mkspec that the Qt library was built with. Previous versions of Qt Creator did not have this problem. The workaround is to manually specify the mkspec to use (in Projects->Build Specs->qmake->Additional arguments). Qt Creator should use the mkspec that the library is built with and not try to make (incorrect) assumptions about which mkspec to use.