Order objects based on LOCAL_SRC_FILES and LOCAL_GENERATED_SOURCES

We have been reordering objects to the linker based on how they were
generated. In soong, they're ordered based on the order listed in the
src_files.

Keep track of which source files created which object files so that we
can create the ordered list. Optionally change the order, based on
BINARY_OBJECTS_ORDER. That way we can compare make and soong builds.

Since we're keeping track of the used source files, warn when an entry
in LOCAL_SRC_FILES is not used. (whether it is an unused file like a
header, or a typo)

LOCAL_GENERATED_SOURCES is not verified, since it is valid to add
headers and other files in that list (to set up dependencies).

Change-Id: I1dfbbb3aa570c11c1db3b7133e46ed0b8c3b8989