Get rid of assumptions about ".nexe" extension.

tests/untrusted_check/nacl.scons

 # -*- python -*-
 # Copyright 2011 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 os
 
 Import('env')
 
-env.ComponentProgram('untrusted_check_test.nexe',
-                     ['untrusted_check_test.c'],
-                     EXTRA_LIBS=['platform',
-                                 'gio',
-                                 'pthread'])
+nexe = env.ComponentProgram('untrusted_check_test',
+                            ['untrusted_check_test.c'],
+                            EXTRA_LIBS=['platform',
+                                        'gio',
+                                        'pthread'])
 
 # nacl-newlib and nacl-glibc's abort() implementations produce
 # different exit codes.
 if env.Bit('nacl_glibc'):
   expected_exit_status = 'untrusted_sigill'
 else:
   expected_exit_status = '1'
 
 node = env.CommandSelLdrTestNacl(
     'untrusted_check_test.out',
-    command = [env.File('untrusted_check_test.nexe')],
+    nexe,
     filter_regex = ('"(Fatal error in file[^/\\\\\\\\]*)'
                     '|(LOG_FATAL.*)'
                     '|(Log output.*)"'),
     filter_group_only = 'true',
     stderr_golden = env.File('untrusted_check_test.stderr'),
     exit_status=expected_exit_status)
 
 env.AddNodeToTestSuite(node, ['small_tests'], 'run_untrusted_check_test')