Require Android SDK copy of CMake to build Vulkan on Android.

platform_tools/android/bin/android_setup.sh

 #!/bin/bash
 ###############################################################################
 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 ###############################################################################
 #
 # android_setup.sh: Sets environment variables used by other Android scripts.
 
@@ skipping 34 matching lines @@
   else
     APP_ARGS=("${APP_ARGS[@]}" "${1}")
   fi
   shift
 done
 
 if [ "$USE_CLANG" == "true" ]; then
   export GYP_DEFINES="skia_clang_build=1 $GYP_DEFINES"
 fi
 
-if [ "$SKIA_VULKAN" == "true" ]; then
-  export GYP_DEFINES="skia_vulkan=1 $GYP_DEFINES"
-fi
-
 function verbose {
   if [[ -n $VERBOSE ]]; then
     echo $@
   fi
 }
 
 function exportVar {
   NAME=$1
   VALUE=$2
   verbose export $NAME=\"$VALUE\"
@@ skipping 13 matching lines @@
      echo "No ANDROID_SDK_ROOT set and can't auto detect it from location of android binary."
      exit 1
   fi
 fi
 
 if [ -z "$ANDROID_HOME" ]; then
   echo "ANDROID_HOME not set so we are setting it to a default value of ANDROID_SDK_ROOT"
   exportVar ANDROID_HOME $ANDROID_SDK_ROOT
 fi
 
+if [ "$SKIA_VULKAN" == "true" ]; then
+  export GYP_DEFINES="skia_vulkan=1 $GYP_DEFINES"
+  # add cmake from the SDK to your path if it doesn't exist
+  if [ ! -d "${ANDROID_SDK_ROOT}/cmake" ]; then
+     echo "The Android SDK Tools version of CMake is required to build Vulkan. ${ANDROID_SDK_ROOT}/cmake"
+     exit 1
+  else
+    export PATH=${ANDROID_SDK_ROOT}/cmake/bin:$PATH
+  fi
+fi
+
 # Helper function to configure the GYP defines to the appropriate values
 # based on the target device.
 setup_device() {
   DEFINES="OS=android"
   DEFINES="${DEFINES} host_os=$(uname -s | sed -e 's/Linux/linux/;s/Darwin/mac/')"
   DEFINES="${DEFINES} skia_os=android"
   DEFINES="${DEFINES} android_base=$(absPath ${SCRIPT_DIR}/..)"
   if [[ "$GYP_DEFINES" != *skia_shared_lib=* ]]; then
       DEFINES="${DEFINES} skia_shared_lib=1"
   fi
@@ skipping 173 matching lines @@
       $ADB $DEVICE_SERIAL shell mkdir -p "$(dirname "$ANDROID_DST")"
       $ADB $DEVICE_SERIAL push $HOST_SRC $ANDROID_DST
     fi
   fi
 
   # turn error checking back on
   set -e
 }
 
 setup_device "${DEVICE_ID}"