fvwm: add pyxdg dependence and enable parallel building

pkgs/applications/window-managers/fvwm/2.6.nix

@@ -17,6 +17,7 @@
 , libxslt
 , perl
 , pkg-config
+, python3Packages
 , readline
 , enableGestures ? false
 }:
@@ -32,7 +33,11 @@ stdenv.mkDerivation rec {
     hash = "sha256-sBVOrrl2WrZ2wWN/r1kDUtR+tPwXgDoSJDaxGeFkXJI=";
   };
 
-  nativeBuildInputs = [ autoreconfHook pkg-config ];
+  nativeBuildInputs = [
+    autoreconfHook
+    pkg-config
+    python3Packages.wrapPython
+  ];
 
   buildInputs = [
     cairo
@@ -48,14 +53,25 @@ stdenv.mkDerivation rec {
     librsvg
     libxslt
     perl
+    python3Packages.python
     readline
   ] ++ lib.optional enableGestures libstroke;
 
+  pythonPath = [
+    python3Packages.pyxdg
+  ];
+
   configureFlags = [
     "--enable-mandoc"
     "--disable-htmldoc"
   ];
 
+  postFixup = ''
+    wrapPythonPrograms
+  '';
+
+  enableParallelBuilding = true;
+
   meta = with lib; {
     homepage = "http://fvwm.org";
     description = "A multiple large virtual desktop window manager";