Set GCC path in makefile

Whenever I am building my package it uses /usr/bin/g++ (System compiler). I want to build my package with c++11 constructs. I have tried -std=c++11 option but with system compiler it says unrecognized option. I want to build my package from a different gcc compiler which will get downloaded as part of my package dependency.

So, How can i specify the location of gcc compiler in Makefile.