Don't continuously rebuild mediaextractor

Use LOCAL_REQUIRED_MODULES instead of LOCAL_ADDITIONAL_DEPENDENCIES to
remove the dependency on a phony module. LOCAL_ADDITIONAL_DEPENDENCIES
also rebuilds the objects when the dependency is dirty, instead of just
making sure mediaextractor-seccomp.policy is installed.

Change-Id: I0d21d4e874b55eadaf5dfb395a85c987392250b3
diff --git a/services/mediaextractor/Android.mk b/services/mediaextractor/Android.mk
index a9a984a..21a75cd 100644
--- a/services/mediaextractor/Android.mk
+++ b/services/mediaextractor/Android.mk
@@ -11,9 +11,7 @@
 
 # service executable
 include $(CLEAR_VARS)
-ifeq ($(TARGET_ARCH), $(filter $(TARGET_ARCH), arm arm64))
-LOCAL_ADDITIONAL_DEPENDENCIES += mediaextractor-seccomp.policy
-endif
+LOCAL_REQUIRED_MODULES_arm := mediaextractor-seccomp.policy
 LOCAL_SRC_FILES := main_extractorservice.cpp minijail/minijail.cpp
 LOCAL_SHARED_LIBRARIES := libmedia libmediaextractorservice libbinder libutils liblog libicuuc libminijail
 LOCAL_STATIC_LIBRARIES := libicuandroid_utils