_86Box: simplify wrapping logic

  # Some libraries are loaded dynamically, but QLibrary doesn't seem to search

  # the runpath, so use a wrapper instead.

  postFixup = let

  preFixup = let

    libPath = lib.makeLibraryPath ([

      libpcap

    ] ++ lib.optional unfreeEnableDiscord discord-gamesdk);

    libPathVar = if stdenv.isDarwin then "DYLD_LIBRARY_PATH" else "LD_LIBRARY_PATH";

  in

  ''

    wrapProgram $out/bin/86Box \

      "''${qtWrapperArgs[@]}" \

      --prefix ${libPathVar} : "${libPath}"

  in ''

    makeWrapperArgs+=(--prefix ${libPathVar} : "${libPath}")

  '';

  # Do not wrap twice.

  dontWrapQtApps = true;

  meta = with lib; {

    description = "Emulator of x86-based machines based on PCem.";

    mainProgram = "86Box";