Cross target tests for libopencm3

libopencm3(http://github.com/libopencm3/libopencm3) pull requests are often hard to review. It can be hard to see the impact on "user" land code, it can be hard to see how the behaviour changes from a->b.

This repository contains testing frameworks I've put together to help with cross target testing, with the aim of making them as automated as possible.

General plan is something like....

make -C libopencm3 clean all -j8

make -C tests/xxx clean all flash test V=1

cd libopencm3

git checkout proposed-new-code

return to step 1

Mileage will vary.