xpra: Also add module paths to xorg-uinput.conf

If uinput is used, xpra will silently replace "xorg.conf" with
"xorg-uinput.conf" in the xorg/xvfb command line before launching
it [1]. We also need to inject the xorg module paths there.

[1] https://github.com/Xpra-org/xpra/blob/337d861d28af03d112d5bd88817a8293c1e0fce0/xpra/x11/vfb_util.py#L231-L235

pkgs/tools/X11/xpra/default.nix

@@ -189,6 +189,7 @@ in buildPythonApplication rec {
   postInstall = ''
     # append module paths to xorg.conf
     cat ${xorgModulePaths} >> $out/etc/xpra/xorg.conf
+    cat ${xorgModulePaths} >> $out/etc/xpra/xorg-uinput.conf
 
     # make application icon visible to desktop environemnts
     icon_dir="$out/share/icons/hicolor/64x64/apps"