octave.buildEnv: fix Exec= line in .desktop file

      addPkgLocalList $out ${octave}

      wrapOctavePrograms "${lib.concatStringsSep " " packages}"

      # We also need to modify the Exec= line of the desktop file, so it will point

      # to the wrapper we generated above.

      rm $out/share/applications # should be a symlink to ${octave}/share/applications

      mkdir $out/share/applications

      substitute \

        ${octave}/share/applications/org.octave.Octave.desktop \

        $out/share/applications/org.octave.Octave.desktop \

        --replace-fail ${octave}/bin/octave $out/bin/octave

     '' + postBuild;

  inherit (octave) meta;