fix(image-factory): install GNU tar

The factory copies updater/*.sh and runs perform_update.sh, which unpacks the
exported rootfs with tar --xattrs. Busybox tar does not know that option, so
the unpack died on "tar: unrecognized option: xattrs".

updater/Dockerfile has installed tar for exactly this reason since it was
written, with the reason in a comment. The factory never did - two images
running the same script, with dependencies that have to be declared twice.
Both lists now point at each other.

Without xattrs the unpacked rootfs would lose its file capabilities, so this is
not a matter of taste: it is why the comment says GNU tar rather than tar.

Signed-off-by: Simon Walz <contact@simonwalz.de>

Author: simonwalz

image-factory/Dockerfile

@@ -8,9 +8,13 @@ ENV container=docker
 
 ENTRYPOINT ["/create_image.sh"]
 
+# tar: GNU tar, needed to restore xattrs when unpacking the exported rootfs.
+# Busybox tar has no xattr support and would silently drop file capabilities.
+# This factory runs updater/perform_update.sh, so it needs everything that
+# script needs - keep this list and updater/Dockerfile's in step.
 RUN apk add --no-cache \
     parted dosfstools btrfs-progs \
-    gptfdisk qemu-img kpartx util-linux jq btrfs-progs bash
+    gptfdisk qemu-img kpartx util-linux jq btrfs-progs bash tar
 
 RUN apk add --no-cache \
     grub-efi grub-bios ovmf || true

updater/Dockerfile

@@ -10,6 +10,8 @@ ENTRYPOINT ["/usr/local/updater/updater.sh"]
 
 # tar: GNU tar, needed to restore xattrs when unpacking the exported rootfs.
 # Busybox tar has no xattr support and would silently drop file capabilities.
+# image-factory/Dockerfile runs the same perform_update.sh - keep the two lists
+# in step.
 RUN apk add --no-cache jq btrfs-progs util-linux bash tar
 
 # Install required packages