mangohud: backport gcc-13 fix

Without the change the build fails on `gcc-13` as:

    $ nix build --impure --expr 'with import ./. {}; mangohud.override { stdenv = gcc13Stdenv; }' -L

    mangohud> In file included from ../tests/../src/amdgpu.h:8,
    mangohud>                  from ../tests/test_amdgpu.cpp:9:
    mangohud> ../tests/../src/overlay_params.h:229:21: error: 'uint32_t' is not a member of 'std'; did you mean 'wint_t'?
    mangohud>   229 |    std::vector<std::uint32_t> fps_limit;
    mangohud>       |                     ^~~~~~~~
    mangohud>       |                     wint_t

pkgs/tools/graphics/mangohud/default.nix

@@ -3,6 +3,7 @@
 , fetchFromGitLab
 , fetchFromGitHub
 , fetchurl
+, fetchpatch
 , substituteAll
 , coreutils
 , curl
@@ -123,6 +124,13 @@ stdenv.mkDerivation (finalAttrs: {
       libdbus = dbus.lib;
       inherit hwdata;
     })
+
+    # Pull gcc-13 build fix for nissing <cstdint>
+    (fetchpatch {
+      name = "gcc-13.patch";
+      url = "https://github.com/flightlessmango/MangoHud/commit/3f8f036ee8773ae1af23dd0848b6ab487b5ac7de.patch";
+      hash = "sha256-qbNywAXAStGiVZ1LA5qZyNp4n28iNUuE4N69zXv2gmM=";
+    })
   ];
 
   postPatch = ''