Add a script for running art standalone.

Change-Id: I0c48856d811c40662a6e4a4782478a0bc8e0f697
diff --git a/tools/art b/tools/art
index 0a6c941..2e3a46e 100755
--- a/tools/art
+++ b/tools/art
@@ -34,8 +34,22 @@
 done
 
 unset ANDROID_PRODUCT_OUT # avoid defaulting dex2oat --host-prefix to target output
+
+function follow_links() {
+  file="$1"
+  while [ -h "$file" ]; do
+    # On Mac OS, readlink -f doesn't work.
+    file="$(readlink "$file")"
+  done
+  echo "$file"
+}
+
+PROG_NAME="$(follow_links "$BASH_SOURCE")"
+PROG_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
+ANDROID_BUILD_TOP="$(cd "${PROG_DIR}/../../../../" ; pwd -P)/"
+ANDROID_HOST_OUT=$PROG_DIR/..
+
 mkdir -p /tmp/android-data/dalvik-cache
-cd $ANDROID_BUILD_TOP
 ANDROID_DATA=/tmp/android-data \
   ANDROID_ROOT=$ANDROID_HOST_OUT \
   LD_LIBRARY_PATH=$ANDROID_HOST_OUT/lib \