Precompiled header in Mac cannot have C++11 features

When using precompiled header, it cannot have c+11 features or the build simply failed. CONFIG += c11 and QMAKE_CXXFLAGS += -std=c+11 have all been tried, but neither will work. Building without a precompiled header works fine, so it must be a bug in the build system.

The command line invoked by the build system is

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -pipe -O2 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.7 -Wall -W -fPIE -I../Qt/5.2.1/clang_64/mkspecs/macx-clang -I../TestPre -I. -x objective-c+-header -c ../TestPre/stable.hpp -o TestPre/objective-c+.pch

. As one can see, there is no -std=c++11 flag passed in.

Precompiled headers works fine in Windows environment. This issue is Mac specific.