Rework the Makefiles to be compatible with binary packages.

extra/nanopb.mk

@@ -0,0 +1,29 @@
+# This is an include file for Makefiles. It provides rules for building
+# .pb.c and .pb.h files out of .proto, as well the path to nanopb core.
+
+# Path to the nanopb root directory
+NANOPB_DIR := $(abspath $(dir $(lastword $(MAKEFILE_LIST)))../)
+
+# Files for the nanopb core
+NANOPB_CORE = $(NANOPB_DIR)/pb_encode.c $(NANOPB_DIR)/pb_decode.c
+
+# Check whether to use binary version of nanopb_generator or the
+# system-supplied python interpreter.
+ifneq "$(wildcard $(NANOPB_DIR)/generator-bin)" ""
+	# Binary package
+	PROTOC = $(NANOPB_DIR)/generator-bin/protoc
+	PROTOC_OPTS = 
+else
+	# Source only or git checkout
+	PROTOC = protoc
+	ifdef windir
+		PROTOC_OPTS = --plugin=nanopb=$(NANOPB_DIR)/generator/protoc-gen-nanopb.bat
+	else
+		PROTOC_OPTS = --plugin=nanopb=$(NANOPB_DIR)/generator/protoc-gen-nanopb
+	endif
+endif
+
+# Rule for building .pb.c and .pb.h
+%.pb.c %.pb.h: %.proto $(wildcard %.options)
+	$(PROTOC) $(PROTOC_OPTS) --nanopb_out=. $<
+