RDK: Set explicit dependency rule for parallel compile.

Change-Id: I0244783da423fccedf8c3f8306fe9a8fcf73b9bd
diff --git a/Makefile b/Makefile
index 82d8602..9a432ab 100644
--- a/Makefile
+++ b/Makefile
@@ -32,9 +32,6 @@
 SC_LDFLAGS+=-Wl,--no-as-needed -lgrpc++_unsecure -lprotobuf -lboost_system -llog -ldl -lrt -lpthread -lstdc++ -pthread
 LDFLAGS+= -Wl,--no-as-needed -llog -ldl -lrt -lpthread -lstdc++ -pthread
 
-%.grpc.pb.cc: %.pb.cc %.pb.h
-	#echo "audio_sevice.grpc.pb.cc depends on audio_service.pb.h which is generated by audio_service.pb.cc"
-
 %.grpc.pb.cc: %.proto
 	$(PROTOC) -I=. -I=$(PROTOC_INC) --grpc_out=. --plugin=protoc-gen-grpc=$(GRPC_CPP_PLUGIN_PATH) $<
 
@@ -53,6 +50,11 @@
 %.o: %.c
 	$(CC) -c $(CFLAGS) -o $@ $<
 
+src/audio_service.grpc.pb.cc: src/audio_service.pb.h
+src/audio_server.cpp: src/audio_service.pb.h src/audio_service.grpc.pb.cc
+src/audio_client.cpp: src/audio_service.pb.h src/audio_service.grpc.pb.cc
+src/audio_if_client.cpp: src/audio_service.pb.h src/audio_service.grpc.pb.cc
+
 all: audio_server libaudio_client.so audio_client_test audio_client_test_ac3 halplay dap_setting speaker_delay digital_mode test_arc start_arc hal_param hal_dump hal_patch master_vol effect_tool
 
 audio_server: $(SERVER_OBJS)