1.6.4 is great! But how do I set -std=gnu++11 for SAM boards

Hello. Thanx for the big improvment. The new dependency and board manager makes life much easier.

I need to turn support for c++11 for a Arduino DUE board in Arduino IDE 1.6.4
I added compiler flag inside /hardware/arduino/avr/platform.txt
Now my project compiles for Uno (AVR) board but does not compile for Due (SAM).

Where did /hardware/arduino/sam/platform.txt go?
How do I set c++11 for SAM boards??