Fix warning: "QT_HAS_BUILTIN" redefined

In file included from ../../include/QtCore/qendian.h:1:0,
                 from D:/dev/qt/5.7/src/qtbase/src/corelib/tools/qstring.cpp:61:
D:/dev/qt/5.7/src/qtbase/src/corelib/global/qendian.h:53:0: warning: "QT_HAS_BUILTIN" redefined
 #  define QT_HAS_BUILTIN(x)     __has_builtin(x)
 ^
In file included from ../../include/QtCore/qcompilerdetection.h:1:0,
                 from D:/dev/qt/5.7/src/qtbase/src/corelib/global/qglobal.h:83,
                 from ../../include/QtCore/qglobal.h:1,
                 from D:/dev/qt/5.7/src/qtbase/mkspecs/win32-g++/qplatformdefs.h:51,
                 from D:/dev/qt/5.7/src/qtbase/tools/configure/configure_pch.h:34:
D:/dev/qt/5.7/src/qtbase/src/corelib/global/qcompilerdetection.h:1209:0: note: this is the location of the previous definition
 #  define QT_HAS_BUILTIN(x)             0
 ^