GN: Build with a custom libc++ when using ASAN, TSAN or MSAN.

build/config/sanitizers/BUILD.gn

Index: build/config/sanitizers/BUILD.gn
diff --git a/build/config/sanitizers/BUILD.gn b/build/config/sanitizers/BUILD.gn
index 59821511cc275b515589f75eb13082b064f8dc85..65b5af202ff988748e9b5f10ea2483410469c995 100644
--- a/build/config/sanitizers/BUILD.gn
+++ b/build/config/sanitizers/BUILD.gn
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/sanitizers/sanitizers.gni")
+
 # Contains the dependencies needed for sanitizers to link into executables and
 # shared_libraries. Unconditionally depend upon this target as it is empty if
 # |is_asan|, |is_lsan|, |is_tsan| and |is_msan| are false.

[earthdok, 2015/05/26 16:43:49]

This comment needs to be updated.

By the way, where is this unconditional dependency declared? The only candidate
I see is in ./build/config/BUILDCONFIG.gn, but that seems to only affect
component builds.

[Sam McNally, 2015/05/27 00:08:15]

Done.
Executables and shared libraries should have a dependency on this target. See
https://code.google.com/p/chromium/codesearch/#search/&q=sanitizers:deps

@@ -13,6 +15,9 @@ group("deps") {
     public_configs = [ ":sanitizer_options_link_helper" ]
     deps += [ ":options_sources" ]
   }
+  if (use_custom_libcxx) {
+    deps += [ "//buildtools/third_party/libc++:libcxx_proxy" ]
+  }
 }
 
 config("sanitizer_options_link_helper") {