[gn build] Port a96443e

Author: llvmgnsyncbot

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

@@ -342,6 +342,7 @@ if (current_toolchain == default_toolchain) {
       "__locale",
       "__mbstate_t.h",
       "__memory/addressof.h",
+      "__memory/allocate_at_least.h",
       "__memory/allocation_guard.h",
       "__memory/allocator.h",
       "__memory/allocator_arg_t.h",