Get rid of assumptions about ".nexe" extension.

tests/environment_variables/nacl.scons

 # -*- python -*-
 # Copyright 2010 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')
 
-env.ComponentProgram('env_var_test.nexe', 'env_var_test.c')
+nexe = env.ComponentProgram('env_var_test', 'env_var_test.c')
 
 nodes = []
 
 nodes.append(env.CommandSelLdrTestNacl(
     'empty_env_var_test.out',
-    command=[env.File('env_var_test.nexe')],
+    nexe,
     stdout_golden=env.File('empty_env.stdout'),
     osenv='LANG=This_variable_should_not_get_passed_through_by_default'))
 
 # Note that Scons has trouble with arguments containing spaces so we
 # avoid example values with spaces.
 example_env_args = [
     '-E', 'FOO=contents_of_foo',
     '-E', 'ANOTHER_VAR=another_environment_variable',
     # For simplicity, sel_ldr does not interpret the strings
     # passed via "-E", so it allows duplicate keys, as well as
     # strings not of the form "KEY=VALUE".  This is in line with
     # how Unix's execve() behaves.  We demonstrate this here, but
     # we could change sel_ldr in the future to remove duplicates
     # or require "KEY=VALUE" strings.
     '-E', 'DUP=duplicated_key_1',
     '-E', 'DUP=duplicated_key_2',
     '-E', 'Technically_we_do_not_need_an_equals_sign_here']
 nodes.append(env.CommandSelLdrTestNacl(
     'nonempty_env_var_test.out',
-    command=[env.File('env_var_test.nexe')],
+    nexe,
     sel_ldr_flags=example_env_args,
     stdout_golden=env.File('nonempty_env.stdout'),
     osenv='LANG=This_variable_should_not_get_passed_through_by_default'))
 
 if not env.IsRunningUnderValgrind():
   env.AddNodeToTestSuite(nodes, ['small_tests'], 'run_env_var_test')