CMake bot script

 - Add CMake v3.3.1 (latest) to DEPS.
 - Add cmake/bot-cmake.sh to bootstrap CMake then build Skia using that.

Works on my Mac and Linux box, both with no system CMake installation.

CMake will be ~100M on disk.  The first bootstrap takes a couple minutes,
and a no-op re-run of bot-cmake.sh takes 15-20 seconds.  I thought about
having bot-cmake.sh fetch CMake instead of DEPS, but I'm not sure I can
handle updates, etc. as robustly as it can.

This will only work on Linux and Mac.  CMake requires an older CMake on
Windows.  It doesn't have an equivalent ./bootstrap there.  Will have to
think about how Windows bots will work!

BUG=skia:4269

Review URL: https://codereview.chromium.org/1339603003
2 files changed