anchor.diff:      ++ optional stdenv.isLinux "--enable-linux-aio"
       ++ optional gtkSupport "--enable-gtk"
       ++ optional xenSupport "--enable-xen"
  +    ++ optional cephSupport "--enable-rbd"
       ++ optional openGLSupport "--enable-opengl"
       ++ optional virglSupport "--enable-virglrenderer"
       ++ optional smbdSupport "--smbd=${samba}/bin/smbd";
  
positive.code: , spiceSupport ? !stdenv.isDarwin, spice, spice-protocol
  , usbredirSupport ? spiceSupport, usbredir
  , xenSupport ? false, xen
  , openGLSupport ? sdlSupport, mesa_noglu, epoxy, libdrm
  , virglSupport ? openGLSupport, virglrenderer
  , smbdSupport ? false, samba
  
negative.code:     ++ optionals usbredirSupport [ usbredir ]
      ++ optionals stdenv.isLinux [ alsaLib libaio libcap_ng libcap attr ]
      ++ optionals xenSupport [ xen ]
      ++ optionals cephSupport [ ceph ]
      ++ optionals openGLSupport [ mesa_noglu epoxy libdrm ]
      ++ optionals virglSupport [ virglrenderer ]
      ++ optionals smbdSupport [ samba ];
  