Extract manifest from packaging image

Also include manifest.txt with, for example, version
info when extracting packages from the packagin image.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

scripts/pull-packages.sh

@@ -55,4 +55,4 @@ docker run --rm \
     -u $(id -u):$(id -g) \
     --entrypoint="bash" \
         ${IMAGE} \
-        -c "cp -R /artifacts/packages/* ${DIST_DIR}"
+        -c "cp --preserve=timestamps -R /artifacts/* ${DIST_DIR}"