Make Javadoc script work again in release mode.
Make Javadoc script work again in release mode.

I broke it with `set -e` in CL 178630375 because it tries to `git rm` a directory that's normally not present.

Also, extend CL 178630375's work to make it possible to run the script again if it fails halfway through, this time by using `cp` instead of `mv`.

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google/truth,google/truth,cgruber/truth,google/truth,cgruber/truth