Extra protobuf-related support

Change-Id: I375d32f0bcb695ccb0603743133034941d584163
diff --git a/core/binary.mk b/core/binary.mk
index 9ebf8c6..88c356a 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -160,6 +160,7 @@
 
 $(proto_generated_cc_sources): PRIVATE_PROTO_INCLUDES := $(TOP)
 $(proto_generated_cc_sources): PRIVATE_PROTO_CC_OUTPUT_DIR := $(proto_generated_cc_sources_dir)
+$(proto_generated_cc_sources): PRIVATE_PROTOC_FLAGS := $(LOCAL_PROTOC_FLAGS)
 $(proto_generated_cc_sources): $(proto_generated_cc_sources_dir)/%.pb.cc: %.proto $(PROTOC)
 	$(transform-proto-to-cc)