allow prebuilts

Change-Id: I93636e63d872195490c9032d24bd6a33e43c373f
disable recovery in Otapackage

Change-Id: I8b33295affc9bfe15b7a6544384536fabdbbe888
Allow a device's own headers to take precedence over global ones

Change-Id: I0d9e4cd9859e6f12a5e66c4f6ddd348c3520d9ff