Change mod_for_test_script to make it work with arm os image.

src/scripts/mod_image_for_test.sh

Index: src/scripts/mod_image_for_test.sh
diff --git a/src/scripts/mod_image_for_test.sh b/src/scripts/mod_image_for_test.sh
index ef783a98d034bab0e049ba06ee2cf362eb89c2ee..fb35572443736b9bcda4a0f7219c3d1d40e927bb 100755
--- a/src/scripts/mod_image_for_test.sh
+++ b/src/scripts/mod_image_for_test.sh
@@ -50,10 +50,6 @@ cleanup_rootfs_mounts() {
     echo "Killing process that has open file on our rootfs: $cmdline"
     ! sudo kill $pid  # Preceded by ! to disable ERR trap.
   done
-  if [[ -d "${ROOT_FS_DIR}/modify_scripts" ]]; then
-    echo "Cleaned up modify_scripts mount"
-    ! sudo umount "${ROOT_FS_DIR}/modify_scripts"
-  fi
 }
 
 cleanup_rootfs_loop() {
@@ -100,15 +96,9 @@ else
 fi
 
 MOD_SCRIPTS_ROOT="${GCLIENT_ROOT}/src/scripts/mod_for_test_scripts"
-sudo mkdir -p "${ROOT_FS_DIR}/modify_scripts"
-
-sudo mount --bind "${MOD_SCRIPTS_ROOT}" "${ROOT_FS_DIR}/modify_scripts"
-
 # Run test setup script inside chroot jail to modify the image
-sudo chroot "${ROOT_FS_DIR}" "/modify_scripts/test_setup.sh"
-
-sudo umount "${ROOT_FS_DIR}/modify_scripts"
-sudo rmdir "${ROOT_FS_DIR}/modify_scripts"
+sudo GCLIENT_ROOT=${GCLIENT_ROOT} ROOT_FS_DIR=${ROOT_FS_DIR} \
+    "${MOD_SCRIPTS_ROOT}/test_setup.sh"
 
 cleanup
 trap - EXIT