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/host_dalvik_java_library.mk b/core/host_dalvik_java_library.mk
index 502016b..9ee1183 100644
--- a/core/host_dalvik_java_library.mk
+++ b/core/host_dalvik_java_library.mk
@@ -133,11 +133,11 @@
 	@echo Building with Jack: $@
 	$(jack-java-to-dex)
 
-# The empty command was added because, without it, make misses the fact the $(built_dex) also
-# change $(full_classes_jack). Looks like it would test the date before running $(built_dex)
-# command.
+# $(full_classes_jack) is just by-product of $(built_dex).
+# The dummy command was added because, without it, make misses the fact the $(built_dex) also
+# change $(full_classes_jack).
 $(full_classes_jack): $(built_dex)
-	@echo
+	$(hide) touch $@
 
 $(LOCAL_BUILT_MODULE): PRIVATE_DEX_FILE := $(built_dex)
 $(LOCAL_BUILT_MODULE): $(built_dex) $(java_resource_sources)