Add ability to blacklist packages from chromeos-base/chromeos.

get_package_list

 #!/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.
 
 # Lists all package dependencies of a particular package.  Useful to find out
 # all packages depended on by chromeos and chromeos-dev.
 
 . "$(dirname "$0")/common.sh"
 
 # Script must be run inside the chroot.
 assert_inside_chroot
 
 get_default_board
 
 # Flags.
 DEFINE_string board "$DEFAULT_BOARD" \
   "The board for which the image was built." b
 
 # Parse flags.
 FLAGS "$@" || exit 1
+eval set -- "${FLAGS_ARGV}"
+
+[[ -z "${FLAGS_board}" ]] && die "A board must be specified."
 
 if [[ -z "${FLAGS_ARGV}" ]]; then
-  echo "Please specify package."
-  echo "Usage:  ./get_package_list.sh chromeos-base/chromeos > package.list"
-  exit 1
+  warn "Please specify package."
+  die "Usage:  ./get_package_list.sh chromeos-base/chromeos > package.list"
 fi
 
 emerge-$FLAGS_board --emptytree --usepkgonly -p -v --columns \
   $1 2> /dev/null | cut -d ' ' -f 8 | grep '/'