Resolve target specification relative to script.

lib/src/rastak.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.md file.
 
 library rasta.rastak;
 
 import 'dart:async' show
     Future;
 
 import 'dart:io' show
     File,
     IOSink;
 
+import 'dart:isolate' show
+    Isolate;
+
 import 'package:compiler/src/common/tasks.dart' show
     CompilerTask;
 
 import 'package:compiler/src/elements/elements.dart' show
     CompilationUnitElement,
     LibraryElement;
 
 import 'package:kernel/ast.dart' as ir;
 
 import 'package:kernel/binary/ast_to_binary.dart' show
@@ skipping 97 matching lines @@
     await sink.close();
   }
   print("Wrote $uri");
 }
 
 Future<Null> main(List<String> arguments, isolateArgument) async {
   Stopwatch wallClock = new Stopwatch()..start();
   Options options = new OptionParser().parse(arguments, Uri.base);
   List<String> compilerOptions =
       options.isVerbose ? <String>['--verbose'] : <String>[];
+  Uri script = await Isolate.resolvePackageUri(
+      Uri.parse("package:rasta/src/rastak.dart"));
+  Uri targetSpecification = Uri.base.resolveUri(script)
+      .resolve("../../dart_vm_standalone.json");
   IoCompilerFactory factory = new IoCompilerFactory(
-      Uri.base.resolve("dart_vm_standalone.json"), compilerOptions,
-      <String, dynamic>{});
+      targetSpecification, compilerOptions, <String, dynamic>{});
   (await factory.diagnostics)
       ..verbose = options.isVerbose
       ..showWarnings = true
       ..throwOnError = true
       ..throwOnErrorCount = 1;
 
   CustomCompiler compiler = await factory.compiler;
   Rastask task = new Rastask(compiler);
   compiler.tasks.add(task);
 
@@ skipping 55 matching lines @@
     await openWrite(options.dependenciesFile, (IOSink sink) {
       void writeCompilationUnit(CompilationUnitElement unit) {
         sink.write("${unit.script.resourceUri}\n");
       }
       kernel.forEachLibraryElement((LibraryElement library) {
         library.compilationUnits.forEach(writeCompilationUnit);
       });
     });
   }
 }