Support to PRODUCT_COPY_FILES.

N/A

A list of words like <source path>:<destination path>[:<owner>]
The file at the source path sould be copied to the destination path
when building this product. <destination path> is relative to
$(PRODUCT_OUT), so it should look like, e.g., "etc/file.xml".
The rules for these copy steps are defined in build/core/Makefile.
The optional :<owner> is used to indicate the owner of a vendor file.

Signed-off-by: liminghao <liminghao@xiaomi.com>