Added utf8_range.c as a source file.

ruby/ext/google/protobuf_c/extconf.rb

@@ -2,6 +2,10 @@
 
 require 'mkmf'
 
+ext_name = "google/protobuf_c"
+
+dir_config(ext_name)
+
 if RUBY_PLATFORM =~ /darwin/ || RUBY_PLATFORM =~ /linux/
   $CFLAGS += " -std=gnu99 -O3 -DNDEBUG -fvisibility=hidden -Wall -Wsign-compare -Wno-declaration-after-statement"
 else
@@ -14,7 +18,11 @@ if RUBY_PLATFORM =~ /linux/
   $LDFLAGS += " -Wl,-wrap,memcpy"
 end
 
-$objs = ["protobuf.o", "convert.o", "defs.o", "message.o",
-         "repeated_field.o", "map.o", "ruby-upb.o", "wrap_memcpy.o"]
+$VPATH << "$(srcdir)/third_party/utf8_range"
+$INCFLAGS << "$(srcdir)/third_party/utf8_range"
+
+$srcs = ["protobuf.c", "convert.c", "defs.c", "message.c",
+         "repeated_field.c", "map.c", "ruby-upb.c", "wrap_memcpy.c",
+         "utf8_range.c"]
 
-create_makefile("google/protobuf_c")
+create_makefile(ext_name)