Using Raspbian Stretch.

I installed gcc-4.9 with specified version. Then I installed arduino (2.1.0.5) which in turn pulled gcc 4.6. When I try to compile [Marlin](https://reprap.org/wiki/Marlin) in it, it says 

> 
> Marlin requires C++11 support (gcc >= 4.7, Arduino IDE >= 1.6.8).
>  Please upgrade your toolchain.
> 
> 
> 

How do I make Arduino IDE use the correct version of GCC?