Add --sdk option.

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;
 
 import 'compiler_context.dart' show CompilerContext;
 
 const Map<String, dynamic> optionSpecification = const <String, dynamic>{
   "--compile-sdk": Uri,
   "--fatal": ",",
   "--output": Uri,
+  "-o": Uri,
   "--packages": Uri,
   "--platform": Uri,
-  "-o": Uri,
+  "--sdk": Uri,
   "--target": String,
   "-t": String,
 };
 
 class CompilerCommandLine extends CommandLine {
   final String programName;
 
   CompilerCommandLine(String programName, List<String> arguments)
       : programName = programName,
         super(arguments,
@@ skipping 18 matching lines @@
       print(computeUsage(programName, verbose));
       exit(0);
     }
 
     if (options.containsKey("-o") && options.containsKey("--output")) {
       return argumentError(usage, "Can't specify both '-o' and '--output'.");
     }
     if (options.containsKey("-t") && options.containsKey("--target")) {
       return argumentError(usage, "Can't specify both '-t' and '--target'.");
     }
+    if (options.containsKey("--compile-sdk") &&
+        options.containsKey("--platform")) {
+      return argumentError(
+          usage, "Can't specify both '--compile-sdk' and '--platform'.");
+    }
     if (programName == "compile_platform" && arguments.length != 3) {
       return argumentError(usage, "Expected three arguments.");
     } else if (arguments.isEmpty) {
       return argumentError(usage, "No Dart file specified.");
     }
   }
 
   Uri get output {
     return options["-o"] ?? options["--output"] ?? defaultOutput;
   }
 
   Uri get defaultOutput => Uri.base.resolve("${arguments.first}.dill");
 
   Uri get platform {
     return options.containsKey("--compile-sdk")
         ? null
         : options["--platform"] ?? Uri.base.resolve("platform.dill");
   }
 
   Uri get packages => options["--packages"] ?? Uri.base.resolve(".packages");
 
-  Uri get sdk => options["--compile-sdk"];
+  Uri get sdk => options["--sdk"] ?? options["--compile-sdk"];
 
   Set<String> get fatal {
     return new Set<String>.from(options["--fatal"] ?? <String>[]);
   }
 
   bool get errorsAreFatal => fatal.contains("errors");
 
   bool get warningsAreFatal => fatal.contains("warnings");
 
   bool get nitsAreFatal => fatal.contains("nits");
@@ skipping 93 matching lines @@
 
   --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.
 """;