One of the complications of setting up a Zephyr development environment, especially on OS X, is having to get and build CrossTool-NG. ARM maintains an official distro and build of gcc and family for Cortex-M and Cortex-R at https://launchpad.net/gcc-arm-embedded, which provides pre-built binaries for Windows, Linux and Mac OS X. 

I created a simple, minimal Makefile.toolchain.gcc-arm-embedded that adds support for this toolchain to Zephyr, see attached patch. If there is interest in accepting this, I can add qemu and OpenOCD to this, as well as update the documentation, as well as generalising/parameterising the paths etc. Please advise how to proceed.

I tested on the frdm_k64f board, with versions 4.9-2015-q2-update and 5.0-2015-q4-major of the toolchain, and with several of the example applications, and they all functioned correctly.

(There is also another hunk in the patch that adds .DS_Store to gitignore -- it's a metadata file generated by the OS X Finder, and can be safely ignored).


(Disclaimer: I work at ARM, but this is a personal contribution).