Fix unused src tracking for generated .o files

*.o files that are passed in via LOCAL_GENERATED_SOURCES are added
directly to all_objects, they are not mixed with the normal_objects that
we track. So omit them from they my_gen_src_files list so that we don't
warn that they're unused.

Change-Id: I94b85504032e70fbcc00207d6200557700dd0a89
diff --git a/core/binary.mk b/core/binary.mk
index f33f676..4f5ced5 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -526,7 +526,7 @@
 # Other files (like headers) are allowed in LOCAL_GENERATED_SOURCES,
 # since other compiled sources may depend on them, and we set up
 # the dependencies.
-my_gen_src_files := $(filter %.c %$(LOCAL_CPP_EXTENSION) %.S %.s %.o,$(my_generated_sources))
+my_gen_src_files := $(filter %.c %$(LOCAL_CPP_EXTENSION) %.S %.s,$(my_generated_sources))
 
 ALL_GENERATED_SOURCES += $(my_generated_sources)