build: Add support for PRODUCT_COPY_FILES_OVERRIDES

 * We may have a case where prebuilts need to be built from
   source instead based on an externalized config.
 * New directive takes a list of destination files to remove from
   PRODUCT_COPY_FILES so that other instructions can be supplied.

Change-Id: I7feff16440e54d1676ffddbbd96d5947efa43ede
qcom_utils: Update list of QCOM_BOARD_PLATFORMS

Add msm8226 (Moto G) and other upcoming platforms
Change-Id: Icf895cbcf86791ca800636a1c0893b3a905a27a0

Conflicts:
	core/qcom_utils.mk