scripts: allow calling cros_generate_update_payload from outside the chroot

cros_generate_update_payload

 #!/bin/bash
 
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to generate a Chromium OS update for use by the update engine.
 # If a source .bin is specified, the update is assumed to be a delta update.
 
 # --- BEGIN COMMON.SH BOILERPLATE ---
 # Load common CrOS utilities.  Inside the chroot this file is installed in
 # /usr/lib/crosutils.  Outside the chroot we find it relative to the script's
 # location.
 find_common_sh() {
-  local common_paths=(/usr/lib/crosutils $(dirname "$(readlink -f "$0")"))
+  local thisdir="$(dirname "$(readlink -f "$0")")"
+  local common_paths=(/usr/lib/crosutils "${thisdir}")
   local path
 
   SCRIPT_ROOT=
   for path in "${common_paths[@]}"; do
     if [ -r "${path}/common.sh" ]; then
       SCRIPT_ROOT=${path}
       break
     fi
   done
+
+  # HACK(zbehan): We have to fake GCLIENT_ROOT in case we're running inside
+  # au_zip enviroment. GCLIENT_ROOT detection became fatal...
+  [ "${SCRIPT_ROOT}" == "${thisdir}" ] && \
+    export GCLIENT_ROOT="."
 }
 
 find_common_sh
 . "${SCRIPT_ROOT}/common.sh" || (echo "Unable to load common.sh" && exit 1)
 # --- END COMMON.SH BOILERPLATE ---
 
-# Need to be inside the chroot to load chromeos-common.sh
-assert_inside_chroot
-
 # Load functions and constants for chromeos-install
-. "/usr/lib/installer/chromeos-common.sh" || \
+# NOTE: Needs to be called from outside the chroot.
+. "/usr/lib/installer/chromeos-common.sh" &> /dev/null || \
+. "${SRC_ROOT}/platform/installer/chromeos-common.sh" &> /dev/null || \
+. "./chromeos-common.sh" || \
   die "Unable to load /usr/lib/installer/chromeos-common.sh"
 
 SRC_MNT=""
 DST_MNT=""
 SRC_KERNEL=""
 SRC_ROOT=""
 DST_KERNEL=""
 DST_ROOT=""
 STATE_MNT=""
 STATE_LOOP_DEV=""
@@ skipping 210 matching lines @@
 
   GENERATOR="${SCRIPTS_DIR}/mk_memento_images.sh"
 
   CROS_GENERATE_UPDATE_PAYLOAD_CALLED=1 "$GENERATOR" "$DST_KERNEL" "$DST_ROOT"
   mv "$(dirname "$DST_KERNEL")/update.gz" "$FLAGS_output"
 
   trap - INT TERM EXIT
   cleanup noexit
   echo "Done generating full update."
 fi