enter_choot: fix breakage some people ran into

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 80 matching lines @@
 
     MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}$CHROOT_TRUNK_DIR")"
     if [ -z "$(mount | grep -F "on $MOUNTED_PATH")" ]
     then
       sudo mount --bind "$FLAGS_trunk" "$MOUNTED_PATH"
     fi
 
     MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}${INNER_CHROME_ROOT}")"
     if [ -z "$(mount | grep -F "on $MOUNTED_PATH")" ]
     then
-      CHROME_ROOT="$(readlink -f "$FLAGS_chrome_root")"
+      ! CHROME_ROOT="$(readlink -f "$FLAGS_chrome_root")"
       if [ -z "$CHROME_ROOT" ]; then
         ! CHROME_ROOT="$(cat "${FLAGS_chroot}${CHROME_ROOT_CONFIG}" \
           2>/dev/null)"
       fi
       if [[ ( -z "$CHROME_ROOT" ) || ( ! -d "${CHROME_ROOT}/src" ) ]]; then
         echo "Not mounting chrome source"
         sudo rm -f "${FLAGS_chroot}${CHROME_ROOT_CONFIG}"
       else
         echo "Mounting chrome source at: $INNER_CHROME_ROOT"
         echo "$CHROME_ROOT" | \
@@ skipping 103 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