Flake update, update oom config, disable avidemux and remove gnome specialization (due to cmake)

nix.nix

@@ -25,6 +25,7 @@
         "nix-command"
         "flakes"
       ];
+      download-buffer-size = 524288000;
       log-lines = 30;
       min-free = mkDefault "${toString (5 * 1024 * 1024 * 1024)}";
       max-free = mkDefault "${toString (10 * 1024 * 1024 * 1024)}";