Dummy SBCL property to allow other derivations to build.

pkgs/development/compilers/sbcl/bootstrap.nix

···
       sha256 = "0sp5445rbvms6qvzhld0kwwvydw51vq5iaf4kdqsf2d9jvaz3yx5";
     };
     armv6l-linux = armv7l-linux;
+    x86_64-solaris = x86_64-linux;
   };
   cfg = options.${stdenv.system};
 in