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

DEPS

@@ -9,6 +9,7 @@ deps = {
   #   - can use use our existing t_p/e/libjpeg instead of pulling it for Android?
 
   "third_party/externals/angle2"  : "https://chromium.googlesource.com/angle/angle.git@f9ac8fea307532e31cba6240801b4a56483591f8",
+  "third_party/externals/cmake"   : "https://cmake.googlesource.com/[email protected]",
   "third_party/externals/freetype": "https://skia.googlesource.com/third_party/freetype2.git@VER-2-5-0-1",
   "third_party/externals/gyp"     : "https://chromium.googlesource.com/external/gyp.git@08429da7955a98ef764fafa223dd7de73f654b2d",
   "third_party/externals/harfbuzz": "https://skia.googlesource.com/third_party/[email protected]",

cmake/cmake_build

@@ -0,0 +1,26 @@
+#!/bin/sh
+# Copyright 2015 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Script for building with CMake on Skia build bots.
+# If you have CMake installed on your system, you can just use it normally.
+
+set -e
+set -x
+
+here=`dirname $0`
+cores=32
+
+echo "Bootstrapping CMake"
+pushd $here/../third_party/externals/cmake
+./bootstrap --parallel=$cores
+make -j $cores
+popd
+
+echo "Building with bootstrapped CMake"
+pushd $here
+../third_party/externals/cmake/bin/cmake . -G Ninja
+ninja skia  # The default also builds `example`, which I'm leaving a TODO for now.
+popd