Stop using dart2dart in Makefile

It has been deprecated for a long time and no longer works in Dart 1.18.

BUG=https://github.com/dart-lang/dart-protoc-plugin/issues/58

Review URL: https://chromiumcodereview.appspot.com//2107023003 .
diff --git a/Makefile b/Makefile
index 3f9c344..bd370d4 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,7 @@
 
 OUTPUT_DIR=out
 PLUGIN_NAME=protoc-gen-dart
-PLUGIN_PATH=$(OUTPUT_DIR)/$(PLUGIN_NAME)
+PLUGIN_PATH=bin/$(PLUGIN_NAME)
 
 BENCHMARK_PROTOS = $(wildcard benchmark/protos/*.proto)
 
@@ -47,16 +47,8 @@
 
 PREGENERATED_SRCS=lib/descriptor.proto lib/plugin.proto
 
-
-$(PLUGIN_PATH): $(PLUGIN_SRC)
-	[ -d $(OUTPUT_DIR) ] || mkdir $(OUTPUT_DIR)
-	# --categories=all is a hack, it should be --categories=Server once dart2dart bug is fixed.
-	dart2js --checked --output-type=dart --show-package-warnings --categories=all -o$(PLUGIN_PATH) bin/protoc_plugin.dart
-	dart prepend.dart $(PLUGIN_PATH)
-	chmod +x $(PLUGIN_PATH)
-
 $(TEST_PROTO_LIBS): $(PLUGIN_PATH) $(TEST_PROTO_SRCS)
-	[ -d $(TEST_PROTO_DIR) ] || mkdir $(TEST_PROTO_DIR)
+	[ -d $(TEST_PROTO_DIR) ] || mkdir -p $(TEST_PROTO_DIR)
 	protoc\
 		--dart_out=$(TEST_PROTO_DIR)\
 		-I$(TEST_PROTO_SRC_DIR)\
diff --git a/bin/protoc-gen-dart b/bin/protoc-gen-dart
new file mode 100755
index 0000000..7b398d0
--- /dev/null
+++ b/bin/protoc-gen-dart
@@ -0,0 +1,2 @@
+#!/bin/bash
+dart bin/protoc_plugin.dart -c "$@"
diff --git a/prepend.dart b/prepend.dart
deleted file mode 100755
index 5ca276f..0000000
--- a/prepend.dart
+++ /dev/null
@@ -1,12 +0,0 @@
-#!/usr/bin/env dart
-import 'dart:io';
-
-main(List<String> arguments) {
-  final fileName = arguments.first;
-  final file = new File(fileName);
-  final content = file.readAsStringSync();
-  file.writeAsStringSync('#!/usr/bin/env dart\n$content');
-  // For development use the line below instead of the one above to
-  // avoid using the dart2dart code.
-  // file.writeAsStringSync('#!/bin/bash\ndart bin/protoc_plugin.dart');
-}