This reduces the amount of required disk space, so we don't hit
the GH CI limits. Note that hex files are kept until the end of
the run for uploading the binaries to an artifact, but they're
quite small compared to all the intermediate data.
This way we avoid having the ARM toolchain as an artifact when
the run ends and it also lets us reuse the cache from different
runs.
Also, make sure the whole file is indented with 2 spaces.
There's no way to trigger CI on push OR PR, since the CI build
on push is triggered immediately and when the PR is created the
push run is already underway.
Also, make some cosmetic changes to the artifact name to include
the date, inav version and git revision.
Add a workflow file which is triggered on every commit, runs the
tests and tries to compile all targets with -Werror.
On each run of the actions, all the built binaries are saved as
build artifacts, so this can be helpful for providing binaries
for testing.
