Use the '--force' argument for copying ramdisk to recovery ramdisk

* sbin/charger is a symlink to healthd now, but some devices
  still use a different custom charger binary, which fails
  to get copied.
* Fix that by using '-f' so that it gets correctly copied.

Change-Id: I3609335533ca7919339f7a4f831c89d486c25583
build: Allow devices to specify a RIL variant

Change-Id: Ia5d35d916be358fb7be7ead6bd05cc3628b35a37
core: Allow to disable block based OTA's

on Xiaomi Mi2, it causes that the user can't install GAPPS because
the filesystem is smaller than the partition then(users resize the syspart).

Change-Id: I1dcde9c9a212c34108629537cb8c1088a0373573