PNaCl: Enable testing of computed gotos, including GCC torture tests

tests/computed_gotos/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('env')
 
-if not env.AllowNonStableBitcode():
-  Return()
-if env.Bit('bitcode'):
-  # Computed gotos are currently not allowed by PNaCl's bitcode ABI.
-  env.Append(LINKFLAGS=['--pnacl-disable-abi-check'])
+if env['TOOLCHAIN_FEATURE_VERSION'] < 4:
+  # In old versions of the PNaCl toolchain, computed gotos are left as
+  # "indirectbr" and "blockaddress", which are not allowed by PNaCl's
+  # stable ABI.
+  if not env.AllowNonStableBitcode():
+    Return()
+  if env.Bit('bitcode'):
+    env.Append(LINKFLAGS=['--pnacl-disable-abi-check'])
 
 # We are testing a GNU C extension which is disallowed by "-pedantic" mode.
 env.FilterOut(CCFLAGS=['-pedantic'])
 
 prog = env.ComponentProgram('computed_goto', 'computed_goto.c',
                             EXTRA_LIBS=['${NONIRT_LIBS}'])
 node = env.CommandSelLdrTestNacl('computed_goto_test.out', prog)
 env.AddNodeToTestSuite(node, ['small_tests'], 'run_computed_goto_test')