Die if we fail to generate Javadoc.
Die if we fail to generate Javadoc.

I saw Javadoc fail a couple times (to be addressed in another CL). AFAICT the full Javadoc was still generated then, but I could imagine bigger problems that mean we don't generate any Javadoc at all, and then possibly we overwrite the existing snapshot Javadoc with an empty site.

Also, make it possible to run the script again after it dies the first time.

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Created by MOE: https://github.com/google/moe
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google/truth,cgruber/truth,google/truth,cgruber/truth,google/truth