Remove the legacy --additional-compiler-flags option from test.py

tools/testing/dart/test_suite.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Classes and methods for enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 690 matching lines @@
         // error should be reported by the compilation command.
       } else if (configuration['runtime'] == 'd8') {
         commands.add(new Command(d8FileName, ['$tempDir/out.js']));
       } else if (configuration['runtime'] == 'jsshell') {
         commands.add(new Command(jsShellFileName, ['$tempDir/out.js']));
       }
       return commands;
 
     case 'dart2dart':
       var compilerArguments = new List.from(args);
-      var additionalFlags =
-          configuration['additional-compiler-flags'].split(' ');
-      for (final flag in additionalFlags) {
-        if (flag.isEmpty) continue;
-        compilerArguments.add(flag);
-      }
       compilerArguments.add('--output-type=dart');
       String tempDir = createOutputDirectory(info.filePath, '');
       compilerArguments.add('--out=$tempDir/out.dart');
       List<Command> commands =
           <Command>[new Command(dartShellFileName, compilerArguments)];
       if (info.hasCompileError) {
         // Do not attempt to run the compiled result. A compilation
         // error should be reported by the compilation command.
       } else if (configuration['runtime'] == 'vm') {
         // TODO(antonm): support checked.
@@ skipping 944 matching lines @@
  * $pass tests are expected to pass
  * $failOk tests are expected to fail that we won't fix
  * $fail tests are expected to fail that we should fix
  * $crash tests are expected to crash that we should fix
  * $timeout tests are allowed to timeout
  * $compileErrorSkip tests are skipped on browsers due to compile-time error
 """;
     print(report);
    }
 }