app2unit: fix missing runtime dependency (#483200)

pkgs/by-name/ap/app2unit/package.nix

@@ -2,10 +2,12 @@
   lib,
   stdenvNoCC,
   dash,
+  xdg-terminal-exec,
   scdoc,
   fetchFromGitHub,
   nix-update-script,
   installShellFiles,
+  withTerminalSupport ? true,
 }:
 stdenvNoCC.mkDerivation (finalAttrs: {
   pname = "app2unit";
@@ -49,6 +51,11 @@ stdenvNoCC.mkDerivation (finalAttrs: {
   postFixup = ''
     substituteInPlace $out/bin/app2unit \
       --replace-fail '#!/bin/sh' '#!${lib.getExe dash}'
+  ''
+  + lib.optionalString withTerminalSupport ''
+    substituteInPlace $out/bin/app2unit \
+      --replace-fail 'A2U__TERMINAL_HANDLER=xdg-terminal-exec' \
+                     'A2U__TERMINAL_HANDLER=${lib.getExe xdg-terminal-exec}'
   '';
 
   meta = {