Fix PDK builds

$OUT/obj/APPS/SystemUI_intermediates/package.dex.apk was not being
written after being converted to Soong.  Add a copy rule for it
to soong_app_prebuilt.mk, add it as an implicit output to the Make
rules that create it, and add it as a real dependency to the
platform.zip rules.

Test: m platform
Change-Id: I96f58d3d80b764a51a6acb87e92498589cfe5c18