Fix bots: partial support for --use-sdk (assumes

pkg/compiler/lib/src/library_loader.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.
 
 library dart2js.library_loader;
 
 import 'dart:async';
 import 'dart:io' show Platform;
 
 import 'package:front_end/front_end.dart' as fe;
@@ skipping 836 matching lines @@
       {bool skipFileWithPartOfTag: false}) {
     return measure(() async {
       var isDill = resolvedUri.path.endsWith('.dill');
       ir.Program program;
       if (isDill) {
         api.Input input = await compilerInput.readFromUri(resolvedUri,
             inputKind: api.InputKind.binary);
         program = new ir.Program();
         new BinaryBuilder(input.data).readProgram(program);
       } else {
+        // TODO(sigmund): remove this hack. Ship platform.dill with the SDK
+        // instead.
+        // Note: this logic only works on development and bot configurations,
+        // but will not work when using dart2js outside the repo.
+        var executableUri = new Uri.file(Platform.resolvedExecutable);
+        Uri platformFile = executableUri.path.endsWith('dart-sdk/bin/dart')
+            ? executableUri.resolve('../../patched_dart2js_sdk/platform.dill')
+            : executableUri.resolve('patched_dart2js_sdk/platform.dill');
         var options = new fe.CompilerOptions()
           ..fileSystem = new CompilerFileSystem(compilerInput)
           ..target = new Dart2jsTarget(new TargetFlags())
           ..compileSdk = true
-          ..linkedDependencies = [
-            // TODO(sigmund): infer the location of platform.dill
-            // once it is shipped as part of the sdk.
-            new Uri.file(Platform.resolvedExecutable)
-                .resolve('patched_dart2js_sdk/platform.dill')
-          ]
+          ..linkedDependencies = [platformFile]
           ..onError = (e) => reportFrontEndMessage(reporter, e);
 
         program = await fe.kernelForProgram(resolvedUri, options);
       }
       if (program == null) return null;
       return createLoadedLibraries(program);
     });
   }
 
   // Only visible for unit testing.
@@ skipping 815 matching lines @@
 }
 
 /// API used by the library loader to synchronously scan a library or
 /// compilation unit and ensure that their library tags are computed.
 abstract class ElementScanner {
   void scanLibrary(LibraryElement library);
   void scanUnit(CompilationUnitElement unit);
 }
 
 const _reuseLibrarySubtaskName = "Reuse library";