[gn build] Port 45d493b

Author: llvmgnsyncbot

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

@@ -1502,6 +1502,7 @@ if (current_toolchain == default_toolchain) {
       "__type_traits/is_reference.h",
       "__type_traits/is_reference_wrapper.h",
       "__type_traits/is_referenceable.h",
+      "__type_traits/is_replaceable.h",
       "__type_traits/is_same.h",
       "__type_traits/is_scalar.h",
       "__type_traits/is_signed.h",