feat(build): added a temporary fix to make test.unit.dart work

Author: vsavkin

tools/broccoli/broccoli-ts2dart.ts

@@ -20,7 +20,8 @@ class TSToDartTranspiler implements DiffingBroccoliPlugin {
  }
 
  rebuild(treeDiff: DiffResult) {
- let toEmit = [];
+ // replace with toEmit = [] once https://github.com/angular/angular/issues/3770 is fixed
+ let toEmit = [path.resolve(this.inputPath, 'angular2/traceur-runtime.d.ts')];
  let getDartFilePath = (path: string) => path.replace(/((\.js)|(\.ts))$/i, '.dart');
  treeDiff.addedPaths.concat(treeDiff.changedPaths)
  .forEach((changedPath) => {