feat(archives): add {archive}.sha256 and construct archives in tmpdir
This is a follow up on @kevr's existing MR 440. Original commit message and title preserved. Follow up marked as fixup.
This change brings some new additions to our archives:
- SHA-256 .sha256 hexdigests
- We construct our archives in a tmpdir now and move them to the archive destination when all are completed. This removes some corrupted downloading when archiving is in-process.
Signed-off-by: Kevin Morris kevr@0cost.org