As suggested by Arnout Vandecappelle, this commit adjusts the
generic-package documentation to document the effect of per-package
directory support on HOST_DIR, STAGING_DIR and TARGET_DIR.
Suggested-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>