Fix uid when tar folder to container

[alanmcanonical]

Details

• Fix uid when tar folder to container
• Use consistent unix-syle option

Rationale

When launching lxd container and creating tarball to send to contain with spread in corporate laptop, the tarball id will be out of container's range:

2026-06-03 11:58:04 Discarding lxd:ubuntu-24.04 (spread-2-ubuntu-24-04), cannot send project content:
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/bin/tar: spread.yaml: Cannot change ownership to uid 1566290747, gid 1566290747: Invalid argument
/bin/tar: tests/fips/task.yaml: Cannot change ownership to uid 1566290747, gid 1566290747: Invalid argument
/bin/tar: tests/fips: Cannot change ownership to uid 1566290747, gid 1566290747: Invalid argument
/bin/tar: tests: Cannot change ownership to uid 1566290747, gid 1566290747: Invalid argument
/bin/tar: Exiting with failure status due to previous errors
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[sergiocazzolato]

Tx