lhapdf: fix "lhapdf list" interactive tool (#44905)

In version 6.2.1 the "list" command now uses python bindings, which need
to be imported, so we need to set the PYTHONPATH.

pkgs/development/libraries/physics/lhapdf/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, python2 }:
+{ stdenv, fetchurl, python2, makeWrapper }:
 
 stdenv.mkDerivation rec {
   name = "lhapdf-${version}";
@@ -9,6 +9,7 @@ stdenv.mkDerivation rec {
     sha256 = "0bi02xcmq5as0wf0jn6i3hx0qy0hj61m02sbrbzd1gwjhpccwmvd";
   };
 
+  nativeBuildInputs = [ makeWrapper ];
   buildInputs = [ python2 ];
 
   enableParallelBuilding = true;
@@ -17,6 +18,10 @@ stdenv.mkDerivation rec {
     pdf_sets = import ./pdf_sets.nix { inherit stdenv fetchurl; };
   };
 
+  postInstall = ''
+    wrapProgram $out/bin/lhapdf --prefix PYTHONPATH : "$(toPythonPath "$out")"
+  '';
+
   meta = {
     description = "A general purpose interpolator, used for evaluating Parton Distribution Functions from discretised data files";
     license     = stdenv.lib.licenses.gpl2;