qtCreator build error : error: explicit instantiation of ‘std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const ... since updating to Mountain Lion

operator << 가 

 error: explicit instantiation of ‘std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]’ but no definition available

이런 에러를 내 뿜을때.. 

$QTDIR/mkspecs/common/g++-macx.conf

에서  -mmacosx-version-min=10.5

의 10.5를 10.7로 고쳐주면 해결!!!