On arm64 the x86 version of corrosion was downloaded. This downloads
the correct version. Also added comments to HACKING.md on how to clean
up a broken cluster as I have done it twice now and forgot how to do it
both times.
Fixes: #284
~~~ shell
% ./ucind cluster create miektest
Cluster "miektest" initialised with machine "machine-1"
Waiting for cluster to be ready... done.
Cluster 'miektest' added to Uncloud config as the current context.
Cluster 'miektest' created.
~~~
`uc machine ls` also works.
Signed-off-by: Miek Gieben <miek@miek.nl>
