Add build rules to generate native DBus interfaces

With this patch, we can now write Android makefiles like:

include $(CLEAR_VARS)
LOCAL_MODULE := dbus-binding-example
LOCAL_SRC_FILES := main.cpp \
                   dbus-service-config.json \
                   org.example.Daemon.Command.dbus.xml \
                   org.example.Daemon.Manager.dbus.xml
include $(BUILD_EXECUTABLE)

This will cause header files defining native DBus interfaces
to be generated.  These can be included from main.cpp to
easily expose object oriented interface over DBus.

Bug: 22608897
Change-Id: Ic4304ac8de77de74d6955ed17789e5477be9a53e