Hi raghurajappa,
I think we are talking about MPC564xL not MPC574xL toolbox right ?
The Toolbox itself comes with a Math library optimized for these 3 compilers, therefore the options exposed in the MATLAB. To add a new compiler is not a trivial task - therefore that should not be used as an approach in this case.
One simple&doable alternative is to use the MBD Toolbox just for the code generation out of the Simulink blocks, then import those C/H files into the IDE that supports your compiler and link the generated code from MATLAB with your compiler specific startup code and linker command files for NXP processor.
The other alternative would be to use GHS - i see they have support for C++ 11: Green Hills Software Announces Compiler 2017
Hope this help!
Daniel