Update Nixpkgs flake input

flake.lock

@@ -3,11 +3,11 @@
     "genode": {
       "flake": false,
       "locked": {
-        "lastModified": 1602243357,
-        "narHash": "sha256-1Q3D8W8xujTW38CxhXvQIFfxeKuLvBoCzmROiMPxVKA=",
+        "lastModified": 1603455398,
+        "narHash": "sha256-/ABZEGffnm6Tp3mem1MbMpL1TQbc+LcprQELvvox0Ks=",
         "owner": "genodelabs",
         "repo": "genode",
-        "rev": "91f82816189c1aad5d03168cc86c4b4946787b5c",
+        "rev": "5be1c793a5c600b37f3df346b7438ad2aced9fc6",
         "type": "github"
       },
       "original": {
@@ -18,16 +18,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1603868764,
-        "narHash": "sha256-WPummiqYWunZJ3sXUN1ez3ww68YZdnR5VhLEttn17Cw=",
-        "owner": "NixOS",
+        "lastModified": 1604174028,
+        "narHash": "sha256-b/AMdA8G3JIgErvqNJD0QwiqeD2LWw+aVFLlL9VQK7Y=",
+        "owner": "ehmry",
         "repo": "nixpkgs",
-        "rev": "5596cbfb9e914989ffe62cf7e21f332acb3b05b9",
+        "rev": "098487ccb89e3771f4a63a3b2faf500c4002f65e",
         "type": "github"
       },
       "original": {
-        "owner": "NixOS",
-        "ref": "release-20.09",
+        "owner": "ehmry",
+        "ref": "genodepkgs",
         "repo": "nixpkgs",
         "type": "github"
       }

flake.nix

@@ -6,7 +6,7 @@
     flake = false;
   };
 
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/release-20.09";
+  inputs.nixpkgs.url = "github:ehmry/nixpkgs/genodepkgs";
 
   outputs = { self, genode, nixpkgs }:
     let

overlay/default.nix

@@ -110,8 +110,6 @@ in {
 
   solo5-tools = callPackage ./solo5-tools { };
 
-  tup = prev.tup.overrideAttrs (attrs: { setupHook = ./tup/setup-hook.sh; });
-
   zlib = overrideHostAttrs zlib (attrs: {
     postInstall = attrs.postInstall or "" + ''
       pushd ''${!outputLib}/lib