build: use /usr/bin/env to call python

Hardcoding the path to python instead of env is not recommended.  This
can break the build in some Linux environments that link /usr/bin/python
to python3.

Change-Id: I4c62eb391acc6d468ce24ac8640834e965e76e78
releasetools: bring back boot.img handling

This is required for galaxysmtd and other devices with custom
boot format.

This partially reverts "releasetools: Properly handle boot images that use dt"

Change-Id: Ib35001c2d9b906067e5a3c84712dc3a283a38cbb
build: Set ccache base to build top

This enables ccache sharing between different build tree paths.

Change-Id: I99636bdd2779a6ccf0649f027e35cf67df44b6ae
build: Add new public keys to recovery

Change-Id: I11dea464297813be36e60c23728dde8893535c46
build: Include an extra device.mk

Change-Id: I4373f78f57c81e46affc2f6a6bc854bf4c3d00db
Merge "build: Set ccache base to build top" into cm-11.0
Don't set CCACHE_BASEDIR if its already set

 * enable use of shared ccache

Change-Id: Ic708a5d5169291d674b167aa2c87bf2c8adaafae
Merge remote-tracking branch 'github/cm-11.0' into HEAD
Revert "releasetools: bring back boot.img handling"

We need to handle recovery building differently for builds
that will be signed

This reverts commit 0b34286101144ab97302e345fd81dda445824c89.