ota: Remove cruft we don't care about

Skip the date check (downgrade to your content), and don't include
recovery in otapackages.
5.0.0 update: We want the recovery patchstuff back
fix up ota_from_target_files symlink detection.
add support for overriding build.prop settings.

Change-Id: Ie4224d608b7bcb0c2087bd77bc954f8f5f9b6495
Use less heap space for dex on 32-bit build hosts

Run dex with -JXmx1024M instead of 2048M if running on a 32-bit host.
Surprisingly this appears to also work for framework and services; if
not, a little fine-tuning will be needed.

This does not change anything for non-32-bit hosts.

Change-Id: I1d87c3e394acc934af6f7770ea54ba265a1df838
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
build: Set ccache base to build top

This enables ccache sharing between different build tree paths.

Change-Id: I99636bdd2779a6ccf0649f027e35cf67df44b6ae