Sanitizers: Roll in 16 months of libcxx and libcxxabi changes.

third_party/libc++abi/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 static_library("libc++abi") {
   sources = [
     "trunk/src/abort_message.cpp",
     "trunk/src/cxa_aux_runtime.cpp",
     "trunk/src/cxa_default_handlers.cpp",
     "trunk/src/cxa_demangle.cpp",
     "trunk/src/cxa_exception.cpp",
     "trunk/src/cxa_exception_storage.cpp",
     "trunk/src/cxa_guard.cpp",
     "trunk/src/cxa_handlers.cpp",
     "trunk/src/cxa_new_delete.cpp",
     "trunk/src/cxa_personality.cpp",
+    "trunk/src/cxa_thread_atexit.cpp",
     "trunk/src/cxa_unexpected.cpp",
     "trunk/src/cxa_vector.cpp",
     "trunk/src/cxa_virtual.cpp",
     "trunk/src/exception.cpp",
     "trunk/src/private_typeinfo.cpp",
     "trunk/src/stdexcept.cpp",
     "trunk/src/typeinfo.cpp",
   ]
   configs -= [
     "//build/config/compiler:chromium_code",
     "//build/config/compiler:no_rtti",
     "//build/config/gcc:no_exceptions",
     "//build/config/gcc:symbol_visibility_hidden",
   ]
   configs += [
     "//build/config/compiler:no_chromium_code",
     "//build/config/compiler:rtti",
     "//buildtools/third_party/libc++:config",
   ]
 }