Use support/scripts/genimage.sh, instead, which prevents duplicating
TARGET_DIR under ${BUILD_DIR}/genimage.tmp/root.
Use a post-build script to copy uEnv.txt to BINARIES_DIR, as made for
beagleboneai.
Keep the post-image script because it is still used by beaglebone_qt5.
Signed-off-by: Carlos Santos <unixmania@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>