Compiling Qt with the depends system is currently broken on OSX with Xcode 8 upstream Qt bug (Xcode 8 is no longer in beta).
This patches qtbase/configure and qtbse/mkspecs/features/mac/default_pre.prf to work around the issue.
Up for discussion wether we patch this now, wait for a 5.6.2 release and move depends to it, or leave this broken until we move to 5.7 / 5.8 in future.