[gn build] Port 2527b07

Author: llvmgnsyncbot

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

@@ -1524,6 +1524,7 @@ if (current_toolchain == default_toolchain) {
       "__type_traits/is_valid_expansion.h",
       "__type_traits/is_void.h",
       "__type_traits/is_volatile.h",
+      "__type_traits/is_within_lifetime.h",
       "__type_traits/lazy.h",
       "__type_traits/make_32_64_or_128_bit.h",
       "__type_traits/make_const_lvalue_ref.h",