Add superbuild files to build external libraries.
ENH: This SuperBuild fetches avr-binutils, avr-gcc and
avr-libc as well as the Arduino SDK.  It then builds
each dependency and create teh exampes firmware.

ENH: Patch binutils size.c and patch the patch.

The latest arduino-cmake uses the flags -C and --mcu which are not
part of the binutils official releases.  A pathc was released by
Atmel but it hasnt reached upstream.
Merge branch 'superbuild'

Conflicts:
	cmake/ArduinoToolchain.cmake