webos-image: Generate ${webos_sysconfdir}/build/image-name

Create ${webos_sysconfdir}/build/image-name during do_rootfs to provide
the value of ${IMAGE_BASENAME} on the device.

[GF-2688] Invent build variable for image name

Open-webOS-DCO-1.0-Signed-off-by: Janne Hurskainen <janne.hurskainen@palm.com>
Open-webOS-DCO-1.0-Signed-off-by: Keith Derrick <keith.derrick@lge.com>

Change-Id: Ia7279890107351665a6f136c5edcf4fa44e5580a
Reviewed-on: https://g2g.palm.com/1773
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Tested-by: Keith Derrick <keith.derrick@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Reviewed-by: Build Verification
nyx-modules: Support new build info variables

Open-webOS-DCO-1.0-Signed-off-by: Pekka Ropo <pekka.ropo@palm.com>

Change-Id: I1e74d443ec99fcd348797b1618143993a58cb7fd
Reviewed-on: https://g2g.palm.com/1776
Tested-by: Pekka Ropo <pekka.ropo@palm.com>
Reviewed-by: Build Verification
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>