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.
@@ -13,6 +15,9 @@ group("deps") {
     public_configs = [ ":sanitizer_options_link_helper" ]
     deps += [ ":options_sources" ]
   }
+  if (use_custom_libcxx) {

[earthdok, 2015/05/25 15:27:59]

Shouldn't this be in a separate GN file?

[Dirk Pranke, 2015/05/25 22:26:43]

Are you suggesting that rather than have deps depend on libcxx_proxy, we should
have other targets depend on libcxx_proxy directly? I'm not sure what the intent
of your question is.

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

Basically, yes. I was trying to say that the sanitizer config is not a good
place to declare this dependency, as libc++ is not directly related to
sanitizers. However, I don't feel strongly about this, especially if it would
require changing a lot of GN configs.

+    deps += [ "//buildtools/third_party/libc++:libcxx_proxy" ]
+  }
 }
 
 config("sanitizer_options_link_helper") {