[web] Remove --dart-sdk flag to dart2wasm compiler (flutter#149129)

Dart2wasm only needs a platform file, which contains the compiled
`dart:*` libraries. There's no need to specify a seperate `--dart-sdk`
option (anymore).

(See also https://dart-review.googlesource.com/c/sdk/+/366821)

Author: mkustermann

packages/flutter_tools/lib/src/build_system/targets/web.dart

@@ -285,7 +285,6 @@ class Dart2WasmTarget extends Dart2WebTarget {
     final File outputWasmFile =
         environment.buildDir.childFile('main.dart.wasm');
     final File depFile = environment.buildDir.childFile('dart2wasm.d');
-    final String dartSdkPath = artifacts.getArtifactPath(Artifact.engineDartSdkPath, platform: TargetPlatform.web_javascript);
     final String platformBinariesPath = artifacts.getHostArtifact(HostArtifact.webPlatformKernelFolder).path;
     final String platformFilePath = environment.fileSystem.path.join(platformBinariesPath, 'dart2wasm_platform.dill');
     final List<String> dartDefines = compilerConfig.renderer.updateDartDefines(
@@ -298,7 +297,6 @@ class Dart2WasmTarget extends Dart2WebTarget {
       'compile',
       'wasm',
       '--packages=.dart_tool/package_config.json',
-      '--extra-compiler-option=--dart-sdk=$dartSdkPath',
       '--extra-compiler-option=--platform=$platformFilePath',
       '--extra-compiler-option=--delete-tostring-package-uri=dart:ui',
       '--extra-compiler-option=--delete-tostring-package-uri=package:flutter',

packages/flutter_tools/lib/src/test/web_test_compiler.dart

@@ -222,7 +222,6 @@ class WebTestCompiler {
       languageVersion: currentLanguageVersion(_fileSystem, Cache.flutterRoot!),
     );
 
-    final String dartSdkPath = _artifacts.getArtifactPath(Artifact.engineDartSdkPath, platform: TargetPlatform.web_javascript);
     final String platformBinariesPath = _artifacts.getHostArtifact(HostArtifact.webPlatformKernelFolder).path;
     final String platformFilePath = _fileSystem.path.join(platformBinariesPath, 'dart2wasm_platform.dill');
     final List<String> dartDefines = webRenderer.updateDartDefines(buildInfo.dartDefines);
@@ -233,7 +232,6 @@ class WebTestCompiler {
       'compile',
       'wasm',
       '--packages=.dart_tool/package_config.json',
-      '--extra-compiler-option=--dart-sdk=$dartSdkPath',
       '--extra-compiler-option=--platform=$platformFilePath',
       '--extra-compiler-option=--multi-root-scheme=org-dartlang-app',
       '--extra-compiler-option=--multi-root=${projectDirectory.childDirectory('test').path}',

packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart

@@ -34,7 +34,6 @@ const List<String> _kDart2WasmLinuxArgs = <String> [
   'compile',
   'wasm',
   '--packages=.dart_tool/package_config.json',
-  '--extra-compiler-option=--dart-sdk=Artifact.engineDartSdkPath.TargetPlatform.web_javascript',
   '--extra-compiler-option=--platform=HostArtifact.webPlatformKernelFolder/dart2wasm_platform.dill',
   '--extra-compiler-option=--delete-tostring-package-uri=dart:ui',
   '--extra-compiler-option=--delete-tostring-package-uri=package:flutter',