Move libc++ configs and flags out of //build/config/sanitizers

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 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.
 
 # =============================================================================
 # WHAT IS THIS FILE?
 # =============================================================================
 #
 # This is the master GN build configuration. This file is loaded after the
 # build args (args.gn) for the build directory and after the toplevel ".gn"
@@ skipping 501 matching lines @@
   "//build/config/compiler:clang_stackrealign",
   "//build/config/compiler:compiler_arm_fpu",
   "//build/config/compiler:compiler_arm_thumb",
   "//build/config/compiler:chromium_code",
   "//build/config/compiler:default_include_dirs",
   "//build/config/compiler:default_optimization",
   "//build/config/compiler:default_stack_frames",
   "//build/config/compiler:default_symbols",
   "//build/config/compiler:no_rtti",
   "//build/config/compiler:runtime_library",
+  "//build/config/libc++:libc++flags",

[brettw, 2017/06/12 17:55:18]

The reason things need to go here is that targets need to opt-out of them. Will
this need to happen? If this capability is not needed, it might be nice to
reference this from somewhere else like the "compiler" config.

[Tom Anderson, 2017/06/16 20:49:50]

I think (maybe) cronet needs to remove it so it can link against the system
libc++ instead

[brettw, 2017/06/19 23:40:26]

Your current patch doesn't implement this. Since we also aren't sure if it will
be necessary, I think we should not be modifying the file and do the sub-config
solution I suggested. Chronet people can move it to here if they need it.

   "//build/config/sanitizers:default_sanitizer_flags",
 ]
 if (is_win) {
   default_compiler_configs += [
     "//build/config/win:default_crt",
     "//build/config/win:lean_and_mean",
     "//build/config/win:nominmax",
     "//build/config/win:unicode",
     "//build/config/win:winver",
     "//build/config/win:vs_code_analysis",
@@ skipping 158 matching lines @@
 set_defaults("component") {
   if (is_component_build) {
     configs = default_shared_library_configs
     if (is_android) {
       configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
     }
   } else {
     configs = default_compiler_configs
   }
 }