Mac: Enable Mach exception handler by default

src/trusted/service_runtime/build.scons

 # -*- python -*-
 # Copyright (c) 2012 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 platform
 import os
 
 Import('env')
 
@@ skipping 622 matching lines @@
 
 nacl_resource_test_exe = env.ComponentProgram('nacl_resource_test',
                                               ['nacl_resource_test.c'],
                                               EXTRA_LIBS=['sel'])
 node = env.CommandTest(
     'nacl_resource_test.out',
     command=[nacl_resource_test_exe])
 env.AddNodeToTestSuite(node, ['small_tests'], 'run_nacl_resource_test')
 
 # Test nacl_signal
-if env.Bit('posix'):
+if env.Bit('linux'):
   if (not env.Bit('coverage_enabled') and
       not env.Bit('target_arm') and
       not env.Bit('target_mips32') and
       not env.IsRunningUnderValgrind()):
     nacl_signal_exe = env.ComponentProgram(
         'nacl_signal_unittest', 'nacl_signal_unittest.c',
         EXTRA_LIBS=['sel'])
     node = env.CommandTest('nacl_signal_unittest.out',
                            command=[nacl_signal_exe])
 
@@ skipping 365 matching lines @@
                        is_broken=is_broken)
 
 dyn_array_test_exe = env.ComponentProgram('dyn_array_test',
                                           ['dyn_array_test.c'],
                                           EXTRA_LIBS=sel_ldr_libs)
 
 node = env.CommandTest('dyn_array_test.out',
                        command=[dyn_array_test_exe])
 
 env.AddNodeToTestSuite(node, ['small_tests'], 'run_dyn_array_test')