platformid: Copy (reflink) rather than use qemu-img snapshots
We can't use backing files since we can't rely on users to have
them.
Another approach would be flattening after, but I think the
copy approach is clearer.
Closes:
@@ -33,8 +33,7 @@ set -x
tmpd=$(mktemp -tdp "$(dirname "${dest}")" gf-platformid.XXXXXX)
tmp_dest=${tmpd}/box.img
-qemu-img create -q -f qcow2 -b "$(realpath "${src}")" "${tmp_dest}"
-# <walters> I commonly chmod a-w VM images
+/usr/lib/coreos-assembler/cp-reflink "${src}" "${tmp_dest}"
chmod u+w "${tmp_dest}"
# Mount everything read-only by default
