experimental/fiddle: update to work again

experimental/fiddle/fiddle_test

 #!/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 Fiddle build bots.
 
 set -e
 set -x
 
 cd "$(dirname "$0")/../.."
 skia_dir="$PWD"
-cores=32
 
-echo "Bootstrapping CMake"
-cmake_dir="${skia_dir}/third_party/externals/cmake"
-cd "$cmake_dir"
-./bootstrap --parallel=$cores
-make -j $cores cmake
+if ! command -v cmake > /dev/null 2>&1 ; then
+    cores=32
+    echo "Bootstrapping CMake"
+    cmake_dir="${skia_dir}/third_party/externals/cmake"
+    cd "$cmake_dir"
+    ./bootstrap --parallel=$cores
+    make -j $cores cmake
+    export PATH="${cmake_dir}/bin:${PATH}"
+fi
 
-echo "Building fiddle bootstrapped CMake"
+echo "Building Skia and Fiddle"
 cd "${skia_dir}/experimental/fiddle"
-export PATH="${cmake_dir}/bin:${PATH}"
 go build fiddler.go
 ./fiddler "$skia_dir"
 ./fiddler "$skia_dir" draw.cpp > /dev/null
 
 echo "cleaning up"
 cd "$skia_dir"
 git clean -fxd cmake experimental/fiddle