[et] Adds a .bat entrypoint for Windows

bin/et.bat

@@ -0,0 +1,40 @@
+@ECHO off
+REM Copyright 2013 The Flutter Authors. All rights reserved.
+REM Use of this source code is governed by a BSD-style license that can be
+REM found in the LICENSE file.
+
+REM ---------------------------------- NOTE ----------------------------------
+REM
+REM Please keep the logic in this file consistent with the logic in the
+REM `et` script in the same directory to ensure that it continues to
+REM work across all platforms!
+REM
+REM --------------------------------------------------------------------------
+
+SETLOCAL ENABLEDELAYEDEXPANSION
+
+FOR %%i IN ("%~dp0..\..") DO SET SRC_DIR=%%~fi
+
+REM Test if Git is available on the Host
+where /q git || ECHO Error: Unable to find git in your PATH. && EXIT /B 1
+
+SET repo_dir=%SRC_DIR%\flutter
+SET engine_tool_dir=%repo_dir%\tools\engine_tool
+
+REM Determine which platform we are on and use the right prebuilt Dart SDK
+IF "%PROCESSOR_ARCHITECTURE%"=="AMD64" (
+    SET dart_sdk_path=%SRC_DIR%\flutter\prebuilts\windows-x64\dart-sdk
+) ELSE IF "%PROCESSOR_ARCHITECTURE%"=="ARM64" (
+    SET dart_sdk_path=%SRC_DIR%\flutter\prebuilts\windows-arm64\dart-sdk
+) ELSE (
+    ECHO "Windows x86 (32-bit) is not supported" && EXIT /B 1
+)
+
+SET dart=%dart_sdk_path%\bin\dart.exe
+
+cd "%engine_tool_dir%"
+
+REM Do not use the CALL command in the next line to execute Dart. CALL causes
+REM Windows to re-read the line from disk after the CALL command has finished
+REM regardless of the ampersand chain.
+"%dart%" --disable-dart-dev bin\et.dart %* & exit /B !ERRORLEVEL!

tools/engine_tool/README.md

@@ -23,7 +23,6 @@ There are currently many missing features. Some overall goals are listed in the
 GitHub issue [here](https://github.com/flutter/flutter/issues/132807). Some
 desirable new features would do the following:
 
-* Support Windows hosts.
 * Add a `doctor` command.
 * Update the engine checkout so that engine developers no longer have to remeber
 to run `gclient sync -D`.

tools/engine_tool/lib/src/commands/command_runner.dart

@@ -41,7 +41,7 @@ final class ToolCommandRunner extends CommandRunner<int> {
   @override
   Future<int> run(Iterable<String> args) async {
     try{
-      return await runCommand(parse(args)) ?? 1;
+      return await runCommand(parse(args)) ?? 0;
     } on FormatException catch (e) {
       environment.logger.error(e);
       return 1;

tools/engine_tool/test/entry_point_test.dart

@@ -0,0 +1,40 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io' as io;
+
+import 'package:engine_repo_tools/engine_repo_tools.dart';
+import 'package:litetest/litetest.dart';
+import 'package:path/path.dart' as path;
+import 'package:platform/platform.dart';
+import 'package:process_runner/process_runner.dart';
+
+void main() {
+  final Engine engine;
+  try {
+    engine = Engine.findWithin();
+  } catch (e) {
+    io.stderr.writeln(e);
+    io.exitCode = 1;
+    return;
+  }
+
+  test('The entry points under bin/ work', () async {
+    const Platform platform = LocalPlatform();
+    final ProcessRunner runner = ProcessRunner();
+    final String exe = platform.isWindows ? '.bat' : '';
+    final String entrypointPath = path.join(
+      engine.flutterDir.path, 'bin', 'et$exe',
+    );
+    final ProcessRunnerResult processResult = await runner.runProcess(
+      <String>[entrypointPath, 'help'],
+      failOk: true,
+    );
+    if (processResult.exitCode != 0) {
+      io.stdout.writeln(processResult.stdout);
+      io.stderr.writeln(processResult.stderr);
+    }
+    expect(processResult.exitCode, equals(0));
+  });
+}