incpath = env.Clone()
incpath.Append(PROTOCPATH = '#multiple_files')
-incpath.NanopbProto("multifile1")
+incpath.NanopbProto(["multifile1", "multifile1.options"])
incpath.NanopbProto("multifile2")
test = incpath.Program(["test_multiple_files.c", "multifile1.pb.c", "multifile2.pb.c"])