webos.inc: Set PACKAGE_ARCH to MACHINE_ARCH even for packagegroups

:Release Notes:
Default PACKAGE_ARCH is now MACHINE_ARCH, so packagegroup which were
TUNE_PKGARCH because of the dependencies now need to be MACHINE_ARCH
as well.

:Detailed Notes:
Default PACKAGE_ARCH was changed in commit
7d5dafb66f38b1be71ebda3f6ac988d95f6ef677

:Testing Performed:
Only build tested.

:QA Notes:
No functional change to image.

:Issues Addressed:
[GF-43076] Set PACKAGE_ARCH of all compiled components to be
           MACHINE_ARCH

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Icf55c9ca50ee66ae6ec39af19fd41feaa09ca2a2
Reviewed-on: https://g2g.palm.com/4053
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>