Correctly set -stdlib=libc++ when building with a custom libc++.

build/config/sanitizers/sanitizers.gni

 # 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.
 
 declare_args() {
   # Compile for Address Sanitizer to find memory bugs.
   is_asan = false
 
   # Compile for Leak Sanitizer to find leaks.
   is_lsan = false
@@ skipping 62 matching lines @@
   sanitizer_coverage_flags = ""
 }
 
 # Args that are in turn dependent on other args must be in a separate
 # declare_args block. User overrides are only applied at the end of a
 # declare_args block.
 declare_args() {
   # Use libc++ (buildtools/third_party/libc++ and
   # buildtools/third_party/libc++abi) instead of stdlibc++ as standard library.
   # This is intended to be used for instrumented builds.
-  use_custom_libcxx = (is_asan && is_linux) || is_tsan || is_msan || is_ubsan ||
-                      is_ubsan_security || use_libfuzzer
+  use_custom_libcxx = (is_asan && is_linux && !is_chromeos) || is_tsan ||
+                      is_msan || is_ubsan || is_ubsan_security || use_libfuzzer
 
   # Enable -fsanitize-coverage.
   use_sanitizer_coverage = use_libfuzzer || sanitizer_coverage_flags != ""
 }
 
 if (use_sanitizer_coverage && sanitizer_coverage_flags == "") {
   sanitizer_coverage_flags = "edge,indirect-calls,8bit-counters"
 }
 
 using_sanitizer = is_asan || is_lsan || is_tsan || is_msan || is_ubsan ||
@@ skipping 11 matching lines @@
 # If you find a use-case where you want to compile a sanitizer in debug mode
 # and have verified it works, ask brettw and we can consider removing it from
 # this condition. We may also be able to find another way to enable your case
 # without having people accidentally get broken builds by compiling an
 # unsupported or unadvisable configurations.
 #
 # For one-off testing, just comment this assertion out.
 assert(
     !is_debug || !(is_msan || is_lsan || is_tsan || is_ubsan || is_ubsan_vptr),
     "Sanitizers should generally be used in release (set is_debug=false).")