Add 'flutter_release' patch_sdk mode to patch_sdk

pkg/front_end/lib/src/fasta/compiler_command_line.dart

 // Copyright (c) 2016, 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.
 
 library fasta.compiler_command_line;
 
 import 'dart:io' show exit;
 
 import 'command_line.dart' show CommandLine, argumentError;
 
@@ skipping 177 matching lines @@
     file names or arguments to the Dart program.
 
   --packages=<file>
     Use package resolution configuration <file>, which should contain a mapping
     of package names to paths.
 
   --platform=<file>
     Read the SDK platform from <file>, which should be in Dill/Kernel IR format
     and contain the Dart SDK.
 
-  --target=none|vm|vmcc|vmreify|flutter
+  --target=none|vm|vm_fasta|vmcc|vmreify|flutter|flutter_fasta|flutter_fasta_release

[ahe, 2017/07/10 13:19:02]

Perhaps we should change this to:

  --target=TARGET
    Specify the target configuration, where TARGET is one of 'none', 'vm',
    'vm_fasta', 'vmcc', 'vmreify', 'flutter', 'flutter_fasta', or
    'flutter_fasta_release'.

[aam, 2017/07/10 22:11:37]

Done.

     Specify the target configuration.
 
   --verify
     Check that the generated output is free of various problems. This is mostly
     useful for developers of this compiler or Kernel transformations.
 
   --dump-ir
     Print compiled libraries in Kernel source notation.
 
   --exclude-source
     Do not include source code in the dill file.
 
   --compile-sdk=<patched_sdk>
     Compile the SDK from scratch instead of reading it from 'platform.dill'.
 
   --sdk=<patched_sdk>
     Location of the SDK sources for use when compiling additional platform
     libraries.
 
   --fatal=errors
   --fatal=warnings
   --fatal=nits
     Makes messages of the given kinds fatal, that is, immediately stop the
     compiler with a non-zero exit-code. In --verbose mode, also display an
     internal stack trace from the compiler. Multiple kinds can be separated by
     commas, for example, --fatal=errors,warnings.
 """;