Improved nothing-to-do-build

- Removed unnecessary dependency of
  "$(my_symlink) :  $(LOCAL_INSTALLED_MODULE)"
  We can generate symlink to nonexistent file.
  Actually in multilib build $(LOCAL_INSTALLED_MODULE) points to file
  that may not be the target file of the symlink and leads to always
  obsolete $(my_symlink) in the above dependnecy.
- Touch by-product in the dummy rule, to make sure the by-product is
  newer than the main-product.

Change-Id: I2f0e0cc197c49f920fa1f6794083b21cdc333c20
diff --git a/core/binary.mk b/core/binary.mk
index 56f8da8..a9b9e65 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -483,6 +483,7 @@
 # This is just a dummy rule to make sure gmake doesn't skip updating the dependents.
 $(rs_generated_cpps) : $(RenderScript_file_stamp)
 	@echo "Updated RS generated cpp file $@."
+	$(hide) touch $@
 
 my_c_includes += $(renderscript_intermediate)
 my_generated_sources += $(rs_generated_cpps)
@@ -535,6 +536,7 @@
 # This is just a dummy rule to make sure gmake doesn't skip updating the dependents.
 $(proto_generated_headers): $(proto_generated_cc_sources_dir)/%.pb.h: $(proto_generated_cc_sources_dir)/%.pb.cc
 	@echo "Updated header file $@."
+	$(hide) touch $@
 
 $(my_prefix)_$(LOCAL_MODULE_CLASS)_$(LOCAL_MODULE)_proto_defined := true
 endif  # transform-proto-to-cc rule included only once