Etherkit OpenOCD Arduino Build Scripts

Derived from the official Arduino GitHub repo. OpenOCD had to be recompiled to support the ATSAMD21G16B used in Empyrean Beta. Instead of using the original scripts for compilation on each separate host machine, they have been rewritten so that they can all be compiled on a single Linux machine with the usual build tools. Details for each below.

The statically-linked binary ends up in the OpenOCD-0.9.0-dev-arduino folder for each of the build scripts.

Linux 64-bit and 32-bit

Uses gcc. Nothing particularly special to note here.

Invocation:

./arch.linux64.build.bash

or

./arch.linux32.build.bash

Windows

Uses mingw-w64 from the Debian/Linux Mint repo.

Invocation:

./arch.win32.build.bash

macOS

Uses clang from the osxcross package (https://github.com/tpoechtrager/osxcross).

Invocation:

./arch.osx.build.bash