anchor.diff:        CommandArtifact artifact) {
       var sdk = _useSdk
           ? Uri.directory(_configuration.buildDirectory).resolve('dart-sdk/')
  -        : Uri.directory(Repository.dir.toNativePath()).resolve('sdk/');
  +        : Uri.directory(Repository.dir.toNativePath()).resolve(
  +            // TODO(38701): Cleanup after merging the forked SDK into mainline.
  +            _configuration.nnbdMode == NnbdMode.legacy ? 'sdk/' : 'sdk_nnbd/');
       var preambleDir = sdk.resolve('lib/_internal/js_runtime/lib/preambles/');
       return runtimeConfiguration.dart2jsPreambles(preambleDir)
         ..add(artifact.filename);
  
positive.code:       : super._subclass(configuration);
  
    String computeCompilerPath() {
      var prefix = 'sdk/bin';
      var suffix = shellScriptExtension;
  
      if (_isHostChecked) {
  
negative.code:   int get timeoutMultiplier => 4;
  
    String computeCompilerPath() {
      var prefix =
          // TODO(38701): Cleanup after merging the forked SDK into mainline.
          _configuration.nnbdMode == NnbdMode.legacy ? 'sdk/bin' : 'sdk_nnbd/bin';
      if (_isHostChecked) {
        if (_useSdk) {
          throw "--host-checked and --use-sdk cannot be used together";
  