Putting this in the WAR dated back to the Maven days, when adding new
binary build targets was prohibitively expensive. Nobody using a
distributed gerrit.war, as opposed to building locally, actually needs
to run this binary.
This binary has a very thin dependency stack and can build in just a few
seconds, rather than having to build all of the server target, JS
bundles, and other slow pieces of gerrit.war just to generate a proto
file.
Change-Id: If6e7d981bdd57b11536ffe990d11789afd232a46
070b20504e