I recently tried to use Qt Creator 1.3.2 / Qt 4.6.2 / gcc 4.4.0 (32-bit version) on Windows 7 (64-bit) to compile an application using some of the experimental C++0x extensions and encountered the following (fatal) error:

This file requires compiler and library support for the upcoming
ISO C++ standard, C++0x. This support is currently experimental, and must be
enabled with the -std=c++0x or -std=gnu++0x compiler options.

In my search for a solution, I came across this thread, and added the following to the .pro file:

CXXFLAGS += -std=c++0x

but that didn't seem to make a difference.

So, I expect there's some tag I need to add to the .pro (project) file, but I've never messed with the gcc compiler switches in Qt / QMake / QtCreator before, and am uncertain about the proper invokation / incantation. So, my question is how do you set gcc compiler switches when using QtCreator / QMake / Qt?