Move c++ configs from buildtools to build/config/c++ [src-side change]

build/config/BUILD.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.
 
 import("//build/config/allocator.gni")
 import("//build/config/c++/c++.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/dcheck_always_on.gni")
@@ skipping 254 matching lines @@
   }
 }
 
 # Dependencies that all executables and shared libraries should have.
 group("exe_and_shlib_deps") {
   public_deps = []
   if (using_sanitizer) {
     public_deps += [ "//build/config/sanitizers:deps" ]
   }
   if (use_custom_libcxx) {
-    public_deps += [ "//buildtools/third_party/libc++:libcxx_proxy" ]
+    public_deps += [ "//buildtools/third_party/libc++" ]
   }
   if (use_afl) {
     public_deps += [ "//third_party/afl" ]
   }
 }
 
 # Executable configs -----------------------------------------------------------
 
 # Windows linker setup for EXEs and DLLs.
 if (is_win) {
@@ skipping 90 matching lines @@
       # variant for each language used in the target).
       precompiled_source = "//build/precompile.cc"
 
       # Force include the header.
       cflags = [ "/FI$precompiled_header" ]
     } else if (is_mac) {
       precompiled_source = "//build/precompile.h"
     }
   }
 }