fix(yocto): avoid preserving source groups during unpack

[WimYedema]

The dstack recipes copy source trees from outside BitBake's work directory. Archive-mode rsync attempts to preserve their group ownership, which can fail when the build user cannot assign the source group.

Disable group preservation while retaining the other archive-mode attributes.

[kvinwang]

Right fix, right scope — these two recipes are the only in-tree places staging a tree from outside WORKDIR, and both do_installs use explicit install -m, so dropping ownership on the staging copy can't reach the packaged image.

One gap, so I pushed a follow-up (fdfdfbd) instead of a round-trip: --no-group only helps while rsync believes it is not super-user. Under rootless docker/podman or sudo os/build.sh, archive mode still applies -o and fails the same way — chown ... Invalid argument (22), exit 23 — and the aborted transfer leaves the file at the temp-file mode (0600) rather than the source mode, so the staged tree goes silently wrong. Verified with rsync 3.2.7: only --no-owner --no-group survives all three privilege setups.

Ownership is meaningless for a WORKDIR staging copy, so the follow-up drops both and adds a short comment above each do_unpack recording why, otherwise this folds back into a bare -a at the next cleanup. -p is kept deliberately — executable bits still matter.

LGTM with that on top.