Toolchain support needs to pass extra flags to compiler to obtain predefined macros

In GccToolChain::predefinedMacros, we have the following code:

        arguments << QLatin1String("-xc++")
                  << QLatin1String("-E")
                  << QLatin1String("-dM")
                  << QLatin1String("-");

This allows getting the predefined macros, but it's incomplete. It needs to pass extra parameters coming from the project itself which may alter the predefined macros, including:

• -std= (to support -std=c++0x)
• -ansi
• -mcpu, -march, -mtune
• -O, -O2, -O3, etc.