Non-SFI mode: Add Linux asynchronous signal support

src/nonsfi/linux/nacl.scons

 # -*- python -*-
 # Copyright (c) 2014 The Native Client 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('env')
 
 if not env.Bit('nonsfi_nacl'):
   Return()
 
 # Specifying the target arch is necessary for using inline assembly.
 if env.Bit('build_x86_32'):
   env.Append(CCFLAGS=['--target=i686-unknown-nacl'])
 elif env.Bit('build_arm'):
   env.Append(CCFLAGS=['--target=armv7a-unknown-nacl-gnueabihf', '-mfloat-abi=hard'])
 else:
   raise Exception('Unsupported architecture')
 env.ComponentLibrary('libnacl_sys_private', ['linux_sys_private.c',
                                              'directory.c',
-                                             'irt_exception_handling.c'])
+                                             'irt_signal_handling.c'])