Use KATI_DEPFILE for .P associated with object files

Also specify "-d keepdepfile" to ninja so .P files won't be
deleted by ninja.

-include for .s files are removed because GCC doesn't
generate .d files for .s files.

Bug: 26839129
Bug: 27886012
Change-Id: If00e93c7a33449ec314a5cdba438475a32979f4e
(cherry picked from commit 4037c422)