GCC 6.1.0 arm-eabi for OS X El Capitan

This is GCC 6.1.0, rebuilt as a cross-compiler from Mac OS X to arm-eabi specifically,

• the Cortex-M3 as found on the Arduino Due
• the Cortex-M4 as found on the STMicroelectronics STM32F4 Discovery and STM32F429I Discovery boards.

The compiler comes with no Ada Runtime System (RTS).
See the Cortex GNAT Run Time Systems project for candidates.