While attempting to clean up the Bazel examples, I noticed that the example
tests don't actually work because they expect a third_party directory. We could
link third_party/ from the top-level bazel directory, but then we'd have
crossing symlinks (base_workspace/tools->tools and
third_party->base_workspace/third_party). Linking everything in one direction
seemed like a better option, but alternative suggestions are welcome.

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