gamemode: fix build w/ glibc-2.36

To correctly find the implementation of `pidfd_open` - which was
introduced in glibc 2.36 - an additional `#include` is needed. The newly
introduced patch adds that.

Failing Hydra build: https://hydra.nixos.org/build/214432977

pkgs/tools/games/gamemode/default.nix

···
     ./preload-nix-workaround.patch
     # Do not install systemd sysusers configuration
     ./no-install-systemd-sysusers.patch
+
+    # fix build with glibc >=2.36 (declaration of pidfd_open)
+    (fetchpatch {
+      url = "https://github.com/FeralInteractive/gamemode/commit/4934191b1928ef695c3e8af21e75781f8591745f.patch";
+      sha256 = "sha256-pWf2NGbd3gEJFwVP/EIJRbTD29V7keTQHy388enktsY=";
+    })
   ];
 
   postPatch = ''