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