AU: Catch terminate signals and block exit if necessary.

SConstruct

 # 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.
 
 import os
 
 # Protobuffer compilation
 def ProtocolBufferEmitter(target, source, env):
   """ Inputs:
           target: list of targets to compile to
@@ skipping 246 matching lines @@
                    omaha_request_params.cc
                    omaha_response_handler_action.cc
                    payload_signer.cc
                    postinstall_runner_action.cc
                    prefs.cc
                    set_bootable_flag_action.cc
                    simple_key_value_store.cc
                    split_file_writer.cc
                    subprocess.cc
                    tarjan.cc
+                   terminator.cc
                    topological_sort.cc
                    update_attempter.cc
                    update_check_scheduler.cc
                    update_metadata.pb.cc
                    utils.cc""")
 main = ['main.cc']
 
 unittest_sources = Split("""action_unittest.cc
                             action_pipe_unittest.cc
                             action_processor_unittest.cc
@@ skipping 67 matching lines @@
                                   delta_generator_main)
 
 http_server_cmd = env.Program('test_http_server', 'test_http_server.cc')
 
 unittest_env = env.Clone()
 unittest_env.Append(LIBS=['gmock', 'gtest'])
 unittest_cmd = unittest_env.Program('update_engine_unittests',
                            unittest_sources + unittest_main)
 Clean(unittest_cmd, Glob('*.gcda') + Glob('*.gcno') + Glob('*.gcov') +
                     Split('html app.info'))