[Mac/GN] Fix gn gen when using_sanitizer=true use_custom_libcxx=true.

build/config/sanitizers/BUILD.gn

 # 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.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/clang/clang.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 24 matching lines @@
 
 group("deps_no_options") {
   if (using_sanitizer) {
     public_configs = [
       # Even when a target removes default_sanitizer_flags, it may be depending
       # on a library that did not remove default_sanitizer_flags. Thus, we need
       # to add the ldflags here as well as in default_sanitizer_flags.
       ":default_sanitizer_ldflags",
     ]
     deps = []
+    public_deps = []
 
     data = [
       "//tools/valgrind/asan/",
     ]
     if (is_win) {
       exe = ".exe"
     } else {
       exe = ""
     }
     data += [ "$clang_base_path/bin/llvm-symbolizer${exe}" ]
     if (is_linux) {
       # llvm-symbolizer needs this.
       data += [ "$clang_base_path/lib/libstdc++.so.6" ]
     }
 
     if (use_prebuilt_instrumented_libraries ||
         use_locally_built_instrumented_libraries) {
       deps += [ "//third_party/instrumented_libraries:deps" ]
     }
     if (use_custom_libcxx) {
-      public_deps = [
-        "//buildtools/third_party/libc++:libcxx_proxy",
-      ]
+      public_deps += [ "//buildtools/third_party/libc++:libcxx_proxy" ]
       data += [ "$root_out_dir/libc++.so" ]
     }
     if (is_mac) {
       data_deps = [
         ":copy_asan_runtime",
       ]
 
-      public_deps = [
-        ":asan_runtime_bundle_data",
-      ]
+      public_deps += [ ":asan_runtime_bundle_data" ]
     }
   }
 }
 
 if (is_mac && using_sanitizer) {
   copy("copy_asan_runtime") {
     sources = [
       "$clang_base_path/lib/clang/$clang_version/lib/darwin/libclang_rt.asan_osx_dynamic.dylib",
     ]
     outputs = [
@@ skipping 358 matching lines @@
 # This allows to selectively disable ubsan_vptr, when needed. In particular,
 # if some third_party code is required to be compiled without rtti, which
 # is a requirement for ubsan_vptr.
 config("default_sanitizer_flags_but_ubsan_vptr") {
   configs = all_sanitizer_configs - [ ":ubsan_vptr_flags" ]
 }
 
 config("default_sanitizer_flags_but_coverage") {
   configs = all_sanitizer_configs - [ ":coverage_flags" ]
 }