ci/bare-metal: Stop fetching the git tree.

ci/bare-metal: Stop fetching the git tree.

Like for LAVA, make the tradeoff of moving the test scripts and data (55k)
into the artifacts in order to make the per-build jobs not have to pull
down the git tree (hundreds of MB when you don't hit a cached container
for your specific user, which I see happen multiple times a day in my CI
runs).

To do this, we have to be a bit more careful in some places about our
working directory potentially being dirty.

Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5393>