message: fix(compiler): make sure to detect paths that start with `rootDir` correctly
  closes
diff: @@ -306,7 +306,7 @@ export class TsCompilerAotCompilerTypeCheckHostAdapter extends
  shouldGenerateFile(fileName: string): {generate: boolean, baseFileName?: string} {
  // TODO(tbosch): allow generating files that are not in the rootDir
  // See https://github.com/angular/angular/issues/19337
  - if (this.options.rootDir && !fileName.startsWith(this.options.rootDir)) {
  + if (this.options.rootDir && !pathStartsWithPrefix(this.options.rootDir, fileName)) {
  return {generate: false};
  }
  const genMatch = GENERATED_FILES.exec(fileName);
  