This is not like, perfect, since it is a manual operation, but we can
automate it in the future. rclone is used, since it seems like awscli is
not (obviously at least?) able to sync directories such that old things
are deleted, and rclone does this thing properly.
Fixes: https://git.lix.systems/lix-project/meta/issues/2
Change-Id: Ia6a46d861342a6d29b22f981ba4e35e79f79e60e
