pureref: force xcb mode for wayland

pureref doesn't ship with a wayland backend and throws and error trying
to launch, this allows it to use XWayland in such situations.

pkgs/by-name/pu/pureref/package.nix

@@ -1,6 +1,7 @@
 {
   lib,
   appimageTools,
+  makeWrapper,
   runCommand,
   curl,
   gnugrep,
@@ -32,11 +33,14 @@ appimageTools.wrapType1 {
   pname = "pureref";
   inherit version;
 
+  nativeBuildInputs = [ makeWrapper ];
+
   src = "${deb}/usr/bin/PureRef";
 
   extraInstallCommands = ''
     mv $out/bin/pureref $out/bin/PureRef
     cp -r ${deb}/usr/share $out
+    wrapProgram $out/bin/PureRef --set QT_QPA_PLATFORM xcb
   '';
 
   meta = with lib; {