write_makefiles: fix paths in BUILD_PREBUILT with destination

 * proprietary-files.txt entries such as
   "-app/TimeService/TimeService.apk:priv-app/TimeService/TimeService.apk" should
   generate a "LOCAL_SRC_FILES := proprietary/priv-app/TimeService/TimeService.apk"
   in the Makefile definition.
 * However, currently, the prefix_match function is being called on the whole
   PRODUCT_PACKAGES_LIST entry (whole line, including ":"), and therefore,
   TimeService.apk would be included in the APPS list instead of PRIV_APPS.
 * Furthermore, because of the incorrect prefix_match, the generated
   LOCAL_SRC_FILES is "proprietary/app/priv-app/TimeService/TimeService.apk",
   which breaks the build because there is no file at that wrong path.
 * The fix is to make the extract function match up with write_product_packages
   by applying the target_file function on all BUILD_PREBUILT source files.

Change-Id: Ib4859b8854db0f2142bb3f28cce8dd25f7141732
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>