Gh-27 fix versioning tag build workflow

[svenrademakers]

fixes #27
Make sure to checkout the whole git history, so that git describe can do its work

[ruslashev]

I was going to mention that resulting filenames have short commit abbreviations in them (e.g. turingpi_v1.0.2-50-g9ce0573c.swu) but then I noticed that this is the intended behavior of git describe, so no issues here.

By the way, why do we retrieve buildroot's ccache?

[svenrademakers]

By the way, why do we retrieve buildroot's cache?

This is an attempt to speed up compilation by downloading ccache objects of a previous workflow run.
At the moment rerun's are the only scenario's we can see significant speedup's. We should experiment a bit more with keys etc to see how we get the best caching performance.