Revert "releasetools: use prebuilt boot image if using a custom boot image makefile"

This reverts commit df81b5c043ee871a51320b9be518d30d24eeee08.
build: get rid of the sparse expand stuff

* i don't see a reason why we are doing this because we never deal
with flashing system img rawly
* This will put useless write on ssd..
* we don't have space on ssd

Change-Id: Icd53d161b8515f5eca238b98ad68515d69caa34f
Fix /system/app/$app.odex not updated issue

$(built_odex) depends on $(LOCAL_BUILT_MODULE) but doesn't have any build
recipe. It is built by the rules of $(LOCAL_BUILT_MODULE) that results in
a subtle bug: $(built_odex) is always newer than $(LOCAL_BUILT_MODULE)
if $(LOCAL_BUILT_MODULE) rebuilt. Therefore 'make' thinks the targets
(/system/app/$app.odex) depending on $(built_odex) don't need to be updated.
It seems an allegedly optimization bug of 'make'.

The simple fix is to explicitly add $(LOCAL_BUILT_MODULE) as a dependency
of $(installed_odex).

Change-Id: Ia62695eeb9a9709f7115301cbf27eb1fd77a1573