Get rid of assumptions about ".nexe" extension.

tests/gc_instrumentation/nacl.scons

 # -*- python -*-
 # Copyright (c) 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('env')
 
 # PNaCl doesn't have -finstrument-for-thread-suspension currently
 if not env.Bit('bitcode'):
   inputs = ['gc_noinst.c']
 
   # Compile gc_instrumentation.c with -finstrument-for-thread-suspension
   env_inst = env.Clone()
   env_inst.Append(CFLAGS=['-finstrument-for-thread-suspension'])
   inputs += env_inst.ComponentObject('gc_instrumentation.c')
 
-  env.ComponentProgram('gc_instrumentation.nexe', inputs,
-                       EXTRA_LIBS=['nacl_dyncode', 'pthread'])
+  nexe = env.ComponentProgram('gc_instrumentation', inputs,
+                              EXTRA_LIBS=['nacl_dyncode', 'pthread'])
 
-  node = env.CommandSelLdrTestNacl(
-        'gc_instrumentation.out',
-        command=[env.File('gc_instrumentation.nexe')] )
+  node = env.CommandSelLdrTestNacl('gc_instrumentation.out', nexe)
 
   env.AddNodeToTestSuite(node, ['small_tests'], 'run_gc_instrumentation_test')