desktop: switch to alacritty as a terminal

nix/overlay.nix

@@ -1,10 +1,8 @@
 self: super:
 
 let
-  nixpkgs-master = import (builtins.fetchTarball {
-    url = "https://github.com/NixOS/nixpkgs-channels/archive/de5fd9e6110489722e8667664dce9fdc17331866.tar.gz";
-    sha256 = "0z1j2pmvn15m2ir2i9l2prr81cq7f1x8xs4cv2s7q4fslz586ghn";
-  }) {};
+  nixpkgs-master = import <nixpkgs-master> {};
+
   # one application requires php5
   nixpkgsWithPhp5 = super.fetchFromGitHub {
     owner = "nixos";
@@ -14,6 +12,7 @@ let
   };
 
 in {
+  alacritty = nixpkgs-master.alacritty;
   podman = nixpkgs-master.podman;
   conmon = nixpkgs-master.conmon;
 
@@ -23,6 +22,16 @@ in {
   slirp4netns = super.callPackage ./pkgs/slirp4netns.nix {};
   staruml = super.callPackage ./pkgs/staruml.nix { inherit (super.gnome2) GConf; libgcrypt = super.libgcrypt_1_5; };
 
+  roxterm = super.stdenv.mkDerivation {
+    name = "roxterm-custom";
+    buildInputs = [ super.makeWrapper ];
+    phases = "installPhase";
+    installPhase = ''
+      makeWrapper ${super.roxterm}/bin/roxterm $out/bin/roxterm \
+        --add-flags "--separate"
+    '';
+  };
+
   busyboxStatic =  super.busybox.override {
     enableStatic = true;
     extraConfig = ''