Fix broken link on github SDK front page

README.md

 # Dart
 
 [Dart][website] is an open-source, scalable programming language, with robust
 libraries and runtimes, for building web, server, and mobile apps.
 
 ## Using Dart
 
 Visit the [dartlang.org][website] to learn more about the
 [language][lang], [tools][tools],
 [getting started][codelab], and more.
 
 Browse [pub.dartlang.org][pubsite] for more packages and libraries contributed
 by the community and the Dart team.
 
 ## Building Dart
 
-Learn how to [get the source](https://github.com/dart-lang/sdk/wiki/Building#getting-the-source)
-and [prepare your machine to build the SDK](https://github.com/dart-lang/sdk/wiki/Preparing-your-machine-to-build-the-Dart-SDK).
+If you want to build Dart yourself, here is a guide to
+[getting the source, preparing your machine to build the SDK, and
+building](https://github.com/dart-lang/sdk/wiki/Building).
 
 There are more documents on our [wiki](https://github.com/dart-lang/sdk/wiki).
 
 ## Contributing to Dart
 
 The easiest way to contribute to Dart is to [file issues][dartbug].
 
 You can also contribute patches, as described in [Contributing][contrib].
 
 ## License
 
 See [LICENSE][license].
 
 [website]: https://www.dartlang.org
 [license]: https://github.com/dart-lang/sdk/blob/master/LICENSE
 [repo]: https://github.com/dart-lang/sdk
 [lang]: https://www.dartlang.org/docs/dart-up-and-running/ch02.html
 [tools]: https://www.dartlang.org/tools/
 [codelab]: https://www.dartlang.org/codelabs/darrrt/
 [dartbug]: http://dartbug.com
 [contrib]: https://github.com/dart-lang/sdk/wiki/Contributing
 [pubsite]: https://pub.dartlang.org