anchor.diff:      libdrm
       libva
       libvpx
  +    libx11
  +    libxrandr
  +    libxrender
       mesa
  +    renderproto
       systemd_lib
       wayland
  -  ] ++ optionals (xorg != null) [
  -    xorg.libX11
  -    xorg.libXrandr
  -    xorg.libXrender
  -    xorg.renderproto
     ];
   
     configureFlags = [
  
positive.code: , libdrm
  , libva
  , libvpx
  , mesa
  , systemd_lib
  , wayland
  , xorg
  
negative.code:     "--disable-examples"
      "--enable-encoders"
      "--${boolEn (libdrm != null)}-drm"
      "--${boolEn (libx11 != null)}-x11"
      "--${boolEn (libx11 != null && mesa != null)}-glx"
      "--${boolEn (wayland != null)}-wayland"
      "--${boolEn (wayland != null && mesa != null)}-egl"
      "--disable-gtk-doc"
  