Adds tls_edit utility which patches irt_core.nexe's TLS usage.

SConstruct

 #! -*- 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 atexit
 import json
 import os
 import platform
 import re
@@ skipping 1233 matching lines @@
   if image:
     return env.SConstructAbsPath(image)
 
   if chrome_irt:
     return nacl_irt_env.File('${STAGING_DIR}/irt.nexe')
   else:
     return nacl_irt_env.File('${STAGING_DIR}/irt_core.nexe')
 
 pre_base_env.AddMethod(GetIrtNexe)
 
+def GetTLSEdit(env):
+  return env['BUILD_ENV'].File('${STAGING_DIR}/tls_edit${PROGSUFFIX}')
+
+pre_base_env.AddMethod(GetTLSEdit)
 
 def CommandValidatorTestNacl(env, name, image,
                              validator_flags=None,
                              validator=None,
                              size='medium',
                              **extra):
   validator = env.GetValidator(validator)
   if validator is None:
     print 'WARNING: no validator found. Skipping test %s' % name
     return []
@@ skipping 2338 matching lines @@
       'linux' : MakeLinuxEnv,
       'linux2': MakeLinuxEnv,
       'darwin': MakeMacEnv,
       }
   if sys.platform not in platform_func_map:
     raise UserError('Unrecognized host platform: %s', sys.platform)
   make_env_func = platform_func_map[sys.platform]
 
   build_env = make_env_func(build_platform)
   build_env['IS_BUILD_ENV'] = True
-  build_env['BUILD_SCONSCRIPTS'] = []
+
+  # Building tls_edit depends on gio, platform, and validator_ragel.
+  build_env['BUILD_SCONSCRIPTS'] = [
+    # KEEP THIS SORTED PLEASE
+    'src/shared/gio/build.scons',
+    'src/shared/platform/build.scons',
+    'src/trusted/validator_ragel/build.scons',
+    ]
 
   # The build environment is only used for intermediate steps and should
   # not be creating any targets. Aliases are used as means to add targets
   # to builds (IE, all_programs, all_libraries...etc.). Since we want to
   # share all of our build scripts but not define any aliases, we should
   # override the alias function and essentially stub it out.
   build_env.Alias = lambda env, target, source=[], actions=None, **kw : []
 
-  dbg_build_env, opt_build_env = GenerateOptimizationLevels(build_env)
+  return build_env
 
-  return opt_build_env
+def LinkBuildEnv(selected_envs):
+  build_env_map = {
+    'opt': opt_build_env,
+    'dbg': dbg_build_env,
+    }
 
-def LinkBuildEnv(selected_envs, build_env):
+  # We need to find the optimization level in order to know which
+  # build environment we want to use
+  opt_level = None
+  for env in selected_envs:
+    if 'OPTIMIZATION_LEVEL' in env:
+      if env['OPTIMIZATION_LEVEL']:
+        opt_level = env['OPTIMIZATION_LEVEL']
+        break
+
+  build_env = build_env_map.get(opt_level, opt_build_env)
   for env in selected_envs:
     env['BUILD_ENV'] = build_env
 
-  # If platform is not the same as the host environment, add the targets
-  #  of the host environment so scons can find them
-  if GetBuildPlatform() != GetTargetPlatform():
+  if (opt_level not in build_env_map or
+      GetBuildPlatform() != GetTargetPlatform()):
     selected_envs.append(build_env)
 
 def DumpEnvironmentInfo(selected_envs):
   if VerboseConfigInfo(pre_base_env):
     Banner("The following environments have been configured")
     for env in selected_envs:
       for tag in RELEVANT_CONFIG:
         assert tag in env, repr(tag)
         print "%s:  %s" % (tag, env.subst(env.get(tag)))
       for tag in MAYBE_RELEVANT_CONFIG:
@@ skipping 45 matching lines @@
 # a separate mode due to the vagaries of scons when we'd really rather it
 # not be, while not requiring that every bot command line using --mode be
 # changed to list '...,nacl,nacl_irt' explicitly.
 if nacl_env in selected_envs:
   selected_envs.append(nacl_irt_env)
 
 # The nacl_irt_test_env requires nacl_env to build things correctly.
 if nacl_irt_test_env in selected_envs and nacl_env not in selected_envs:
   selected_envs.append(nacl_env)
 
-
 DumpEnvironmentInfo(selected_envs)
 LinkTrustedEnv(selected_envs)
-LinkBuildEnv(selected_envs, MakeBuildEnv())
+
+# When building nacl, any intermediate build tool that is used during the
+# build process must be built using the current build environment, not the
+# target. Create a build environment for this purpose and link it into
+# the selected environments
+dbg_build_env, opt_build_env = GenerateOptimizationLevels(MakeBuildEnv())
+LinkBuildEnv(selected_envs)
+
 # This must happen after LinkTrustedEnv, since that is where TRUSTED_ENV
 # is finally set, and env.UsingEmulator() checks TRUSTED_ENV for the emulator.
 # This must also happen before BuildEnvironments.
 PnaclSetEmulatorForSandboxedTranslator(selected_envs)
 
 BuildEnvironments(selected_envs)
 
 # Change default to build everything, but not run tests.
 Default(['all_programs', 'all_bundles', 'all_test_programs', 'all_libraries'])
 
 
 # Sanity check whether we are ready to build nacl modules
 # NOTE: this uses stuff from: site_scons/site_tools/naclsdk.py
 if nacl_env.Bit('naclsdk_validate') and (nacl_env in selected_envs or
                                          nacl_irt_env in selected_envs):
   nacl_env.ValidateSdk()
 
 if BROKEN_TEST_COUNT > 0:
   msg = "There are %d broken tests." % BROKEN_TEST_COUNT
   if GetOption('brief_comstr'):
     msg += " Add --verbose to the command line for more information."
   print msg
 
 # separate warnings from actual build output
 Banner('B U I L D - O U T P U T:')