Add a --to option to build_image

src/scripts/enter_chroot.sh

 #!/bin/bash
 
 # Copyright (c) 2009 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 enter the chroot environment
 
 # Load common constants.  This should be the first executable line.
 # The path to common.sh should be relative to your script's location.
@@ skipping 66 matching lines @@
     echo "Mounting chroot environment."
 
     # Mount only if not already mounted
     MOUNTED_PATH="$(readlink -f "$FLAGS_chroot/proc")"
     if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
     then
       sudo mount none -t proc "$MOUNTED_PATH" || \
           die "Could not mount $MOUNTED_PATH"
     fi
 
+    MOUNTED_PATH="$(readlink -f "$FLAGS_chroot/sys")"
+    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    then
+      sudo mount none -t sysfs "$MOUNTED_PATH" || \
+          die "Could not mount $MOUNTED_PATH"
+    fi
+
     MOUNTED_PATH="$(readlink -f "$FLAGS_chroot/dev/pts")"
     if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
     then
       sudo mount none -t devpts "$MOUNTED_PATH" || \
           die "Could not mount $MOUNTED_PATH"
     fi
 
     MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}$CHROOT_TRUNK_DIR")"
     if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
     then
@@ skipping 126 matching lines @@
 
 # Run command or interactive shell.  Also include the non-chrooted path to
 # the source trunk for scripts that may need to print it (e.g.
 # build_image.sh).
 sudo chroot "$FLAGS_chroot" sudo -i -u $USER $CHROOT_PASSTHRU \
   EXTERNAL_TRUNK_PATH="${FLAGS_trunk}" LANG=C "$@"
 
 # Remove trap and explicitly unmount
 trap - EXIT
 teardown_env