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: I01d899b862c728036310c35d1ca0d6a224f3ac68
Merge "build: Add support for PRODUCT_COPY_FILES_OVERRIDES" into illusion-4.4