Add nacl-clang testing to SCons

tests/stubout_mode/nacl.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('env')
 
 if 'TRUSTED_ENV' not in env:
   Return()
 
 # Even if stubout mode is not supported sel_ldr still must run valid .nexes.
 # TODO(shyamsundarr): consider removing support for stubout mode completely
 # from code, given that currently only MIPS supports it and it is untested.
 hello_world_nexe = env.File('${STAGING_DIR}/hello_world${PROGSUFFIX}')
 node = env.CommandSelLdrTestNacl(
     'hello_world_stub_out_run.out', hello_world_nexe,
     sel_ldr_flags=['-s'])
 env.AddNodeToTestSuite(
     node, ['small_tests'], 'run_valid_nexe_with_stubout_test')
 
 # Do not run these tests with pexes, assuming they are portable, since
 # they use inline assembler.
 if env.Bit('bitcode') and env.Bit('pnacl_generate_pexe'):
   Return()
 
+# nacl-clang currently has trouble with the top-level asm in this file:
+# https://code.google.com/p/nativeclient/issues/detail?id=3968
+if env.Bit('nacl_clang'):
+  Return()
+
 # The file partly_invalid.c contains inline assembler
 if env.Bit('bitcode'):
   env.AddBiasForPNaCl()
   env.PNaClForceNative()
 
 # Newlib + PIC doesn't provide native ___tls_get_addr, so gold complains.
 if env.Bit('bitcode') and env.Bit('nacl_pic'):
   Return()
 
 # TODO(mseaborn): Extend the ARM validator to support this.
@@ skipping 29 matching lines @@
     exit_status=validation_failure_status)
 env.AddNodeToTestSuite(node, test_suites, 'run_without_stubout_1_test',
                        is_broken=is_validation_disabled)
 
 # With "-c", the executable runs to completion but is not safe.
 node = env.CommandSelLdrTestNacl(
     'partly_invalid_2.out', partly_invalid_nexe,
     stdout_golden=env.File('without_stubout.stdout'),
     sel_ldr_flags=['-c'])
 env.AddNodeToTestSuite(node, test_suites, 'run_without_stubout_2_test')