image.bbclass: add do_rootfs vardeps for {COMPRESS, IMAGE}_CMD_*
We want do_rootfs to rerun if the fstype or compression commands or
dependencies change for any of our configured fstypes (IMAGE_FSTYPES).
IMAGE_TYPEDEP isn't explicitly handled, as it's traversed already, so the end
result will change if it does, and we only really care about the results, not
how we got there. This uses oe.image.Image()._get_image_types() to get the
info about the image and compression types in use.
Signed-off-by: Christopher Larson <chris_larson@mentor.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
