Remove support for old way of building and running unit tests

build_tests.sh

-#!/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.
-
-# Load common constants.  This should be the first executable line.
-# The path to common.sh should be relative to your script's location.
-. "$(dirname "$0")/common.sh"
-
-assert_not_root_user
-restart_in_chroot_if_needed $*
-get_default_board
-
-# Flags
-DEFINE_string build_root "$DEFAULT_BUILD_ROOT"                \
-  "Root of build output"
-DEFINE_string board "$DEFAULT_BOARD" \
-  "Target board for which tests are to be built"
-
-# Parse command line
-FLAGS "$@" || exit 1
-eval set -- "${FLAGS_ARGV}"
-
-if [ -z "$FLAGS_board" ]; then
-  echo Error: --board required
-  exit 1
-fi
-
-# Die on error; print commands
-set -e
-
-TEST_DIRS="
-  cryptohome
-  metrics
-  pam_google
-  window_manager
-  "
-
-sudo TEST_DIRS="${TEST_DIRS}" \
-  emerge-${FLAGS_board} chromeos-base/chromeos-unittests