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

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.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/toolchain/toolchain.gni")
 
 declare_args() {
   # Compile for Address Sanitizer to find memory bugs.
@@ skipping 109 matching lines @@
   is_ubsan = false
   is_ubsan_null = false
   is_ubsan_no_recover = false
   is_ubsan_security = false
   is_ubsan_vptr = false
   msan_track_origins = 0
   sanitizer_coverage_flags = ""
   use_afl = false
   use_cfi_diag = false
   use_cfi_recover = false
-  use_custom_libcxx = false
   use_drfuzz = false
   use_libfuzzer = false
   use_prebuilt_instrumented_libraries = false
   use_locally_built_instrumented_libraries = false
   use_sanitizer_coverage = false
 }
 
 # 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_chromeos &&
-       (!is_chromecast || is_cast_desktop_build)) || is_tsan || is_msan ||
-      is_ubsan || is_ubsan_security || (use_libfuzzer && !is_mac) || use_afl
-
   # Enable -fsanitize-coverage.
   use_sanitizer_coverage =
       use_libfuzzer || use_afl || sanitizer_coverage_flags != ""
 
   # Detect overflow/underflow for global objects.
   #
   # Mac: http://crbug.com/352073
   asan_globals = !is_mac
 }
 
@@ skipping 48 matching lines @@
 
 # ASAN build on Windows is not working in debug mode. Intercepting memory
 # allocation functions is hard on Windows and not yet implemented in LLVM.
 assert(!is_win || !is_debug || !is_asan,
        "ASan on Windows doesn't work in debug (set is_debug=false).")
 
 # Make sure that if we recover on detection (i.e. not crash), diagnostics are
 # printed.
 assert(!use_cfi_recover || use_cfi_diag,
        "Only use CFI recovery together with diagnostics.")