fix script so that the error is actually printed if ant is not installed

platform_tools/android/bin/android_setup.sh

 #!/bin/bash
 #
 # android_setup.sh: Sets environment variables used by other Android scripts.
 
 # Parse the arguments for a DEVICE_ID.
 DEVICE_ID=""
 DEVICE_SERIAL=""
 while (( "$#" )); do
   if [[ $(echo "$1" | grep "^-d$") != "" ]];
   then
@@ skipping 36 matching lines @@
   if [ -z "$ANDROID_TOOL" ]; then
     echo "ERROR: Please define ANDROID_SDK_ROOT in your environment to point"
     echo "       to a valid Android SDK installation."
     exit 1
   fi
   ANDROID_SDK_ROOT=$(cd $(dirname "$ANDROID_TOOL")/.. && pwd)
   exportVar ANDROID_SDK_ROOT "$ANDROID_SDK_ROOT"
 fi
 
 # ant is required to be installed on your system and in your PATH
-ant -version &> /dev/null
+which ant &> /dev/null
 if [[ "$?" != "0" ]]; then
   echo "ERROR: Unable to find ant. Please install it before proceeding."
   exit 1
 fi
 
 # check to see that gclient sync ran successfully
 THIRD_PARTY_EXTERNAL_DIR=${SCRIPT_DIR}/../third_party/externals
 if [ ! -d "$THIRD_PARTY_EXTERNAL_DIR" ]; then
         echo ""
         echo "ERROR: Unable to find the required third_party dependencies needed to build."
@@ skipping 262 matching lines @@
   else
     $ADB $DEVICE_SERIAL push $HOST_SRC $ANDROID_DST
   fi
 }
 
 # Set up the device.
 setup_device "${DEVICE_ID}"
 if [[ "$?" != "0" ]]; then
   exit 1
 fi