Move libcpp_is_static into //build/config/c++ [buildtools changes]

third_party/libc++/BUILD.gn

Index: third_party/libc++/BUILD.gn
diff --git a/third_party/libc++/BUILD.gn b/third_party/libc++/BUILD.gn
index 12da5c43c263ab31d0975beb1c58aafab3088a25..bf373e24b4c3fba1a49febf3ac432de53644b87a 100644
--- a/third_party/libc++/BUILD.gn
+++ b/third_party/libc++/BUILD.gn
@@ -2,14 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/c++/c++.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
 
-# Sanitizer builds need to override operator new, operator delete, and
-# some exception handling symbols, so libc++ must be a shared library
-# to prevent duplicate symbol errors when linking.
-libcpp_is_static = !is_component_build && !using_sanitizer
-
 # Used by libc++ and libc++abi.
 config("config") {
   defines = [ "LIBCXX_BUILDING_LIBCXXABI" ]