Adds changes to unittest scripts to use ebuild if board is specified

src/scripts/build_tests.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.
 
 # 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_inside_chroot
 assert_not_root_user
 
 # Flags
+DEFINE_string build_root "$DEFAULT_BUILD_ROOT"                \
+  "Root of build output"
+DEFINE_string board "" "Target board for which tests are to be built"
 
 # Parse command line
 FLAGS "$@" || exit 1
 eval set -- "${FLAGS_ARGV}"
 
 # Die on error; print commands
 set -e
 
-PLATFORM_DIR="$SRC_ROOT/platform"
-PLATFORM_DIRS="pam_google window_manager cryptohome"
+TEST_DIRS="pam_google window_manager cryptohome"
 
-# Build tests
-for i in $PLATFORM_DIRS
-do
-  echo "building $PLATFORM_DIR/$i"
-  cd "$PLATFORM_DIR/$i"
-  ./make_tests.sh
-  cd -
-done
+if [ -n "$FLAGS_board" ]
+then  
+  sudo TEST_DIRS="${TEST_DIRS}" \
+    emerge-${FLAGS_board} chromeos-base/chromeos-unittests
+else 
+  PLATFORM_DIR="$SRC_ROOT/platform"  
+  
+  # Build tests
+  for i in ${TEST_DIRS}
+  do
+    echo "building $PLATFORM_DIR/$i"
+    cd "$PLATFORM_DIR/$i"
+    OUT_DIR="${FLAGS_build_root}/x86/tests" ./make_tests.sh
+    cd -
+  done
 
-echo "All tests built."
+  echo "All tests built."
+fi