-Fast bot upgrades
- GCC -> Clang;
- Add a Perf bot.
This -Fast mode is a stand-in for "how clients should/do really release code". Today everyone uses Clang, so we should probably switch this bot too.
I also got interested in how it compares in performance to our ordinary Release build, so I've added a Perf bot.
I did try turning on link-time optimization (much slower build, somewhat faster binary), but that failed at the link step. Going to save that for later.
Reviewed-by: Ben Wagner <email@example.com>
Commit-Queue: Mike Klein <firstname.lastname@example.org>