Apple clang version 4.0 not able to build objective-c file (.mm) that includes QDebug

I started to see this issue since 5.4. no problem with 5.3.1

basically we have some .mm obj-c files in our project to do some mac specific functions. we rely on qdebug for debug output. including <QDebug> inside a .mm file works fine with Qt5.3.1

but since 5.4, I saw this issue:

107 In file included from EventHandler.mm:3:
108 In file included from /build/sw/grid/tools/Qt/Qt5.4.0/mac_clang64/lib/QtCore.framework/Versions/5/Headers/QDebug:1:
109 In file included from /build/sw/grid/tools/Qt/Qt5.4.0/mac_clang64/lib/QtCore.framework/Versions/5/Headers/qdebug.h:42:
110 In file included from /buiild/sw/grid/tools/Qt/Qt5.4.0/mac_clang64/lib/QtCore.framework/Headers/qtextstream.h:37:
111 In file included from /build/sw/grid/tools/Qt/Qt5.4.0/mac_clang64/lib/QtCore.framework/Headers/qiodevice.h:39:
112 In file included from /build/sw/grid/tools/Qt/Qt5.4.0/mac_clang64/lib/QtCore.framework/Headers/qobject.h:48:
113 /build/sw/grid/tools/Qt/Qt5.4.0/mac_clang64/lib/QtCore.framework/Headers/qmetatype.h:1943:1: error: copying variable of type 'QBasicAtomicInt' (aka 'QBasicAtomicInteger') invokes deleted constructor