Update from https://crrev.com/311076

build/sanitizers/sanitizers.gyp

 # Copyright 2014 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.
 
 {
   'targets': [
     {
       'target_name': 'sanitizer_options',
       'type': 'static_library',
       'toolsets': ['host', 'target'],
@@ skipping 10 matching lines @@
       'include_dirs': [
         '../..',
       ],
       # Some targets may want to opt-out from ASan, TSan and MSan and link
       # without the corresponding runtime libraries. We drop the libc++
       # dependency and omit the compiler flags to avoid bringing instrumented
       # code to those targets.
       'conditions': [
         ['use_custom_libcxx==1', {
           'dependencies!': [
-            '../../third_party/libc++/libc++.gyp:libcxx_proxy',
+            '../../buildtools/third_party/libc++/libc++.gyp:libcxx_proxy',
           ],
         }],
         ['tsan==1', {
           'sources': [
             'tsan_suppressions.cc',
           ],
         }],
       ],
       'cflags/': [
         ['exclude', '-fsanitize='],
@@ skipping 31 matching lines @@
             'files': [
               '<(llvm_symbolizer_path)',
             ],
           }],
         }],
       ],
     },
   ],
 }