[Qt-creator] QMAKE_CXXFLAGS += -Wno-multichar doesn't work on Mac

[variadic.template]

The trick is to get the -Wno-*-flags behind the -Wall-flag that gets added
by the spec-file, i think. This can be achieved by the  
QMAKE_CFLAGS_WARN_ON/
QMAKE_CFLAGS_WARN_OFF-variables within the pro-file. Worked for me on
Mac.

> So I need to suppress multi-character warning in one of the header
> files. I tried #pragma GCC diagnostic ignored "-Wmultichar" thinking it
> will just disable the warning for that file. It didn't work on either
> Mac or Windows. I may have misunderstood what it mean but on to the next
> option.
>
> I then add QMAKE_CXXFLAGS += -Wno-multichar to my pro file, which will
> disable that warning for all of my files. Not great. But at least it
> will make those warnings go away.
>
> It does. Only on Windows. However I tried, the same warnings persist on
> Mac. I checked the compile output and it is indeed part of the g++ call.
>
> So what's going on? How do I suppress the particular warning?
>
> Thanks.
>
> PS. This is with Creator 2.2 snapshots and Qt 4.7.2.
>