Without the change `wesnoth` fails to build against `gcc-13` as:
$ nix build --impure --expr 'with import <nixpkgs> {}; wesnoth.override { stdenv = gcc13Stdenv; }' -L
In file included from /build/source/src/serialization/base64.cpp:16:
/build/source/src/serialization/base64.hpp:23:49: error: 'uint8_t' was not declared in this scope
23 | using byte_string_view = std::basic_string_view<uint8_t>;
| ^~~~~~~
/build/source/src/serialization/base64.hpp:20:1: note: 'uint8_t' is defined in header '<cstdint>'; did you forget to '#include <cstdint>'?
19 | #include <vector>
+++ |+#include <cstdint>
20 |