sbcl: update to 2.1.2 and add arm64-darwin

(cherry picked from commit 49d2ad093ecd54f40550745f240dda8dbf0ce920)

pkgs/development/compilers/sbcl/common.nix

@@ -2,7 +2,7 @@
 
 { lib, stdenv, fetchurl, writeText, sbclBootstrap
 , sbclBootstrapHost ? "${sbclBootstrap}/bin/sbcl --disable-debugger --no-userinit --no-sysinit"
-, threadSupport ? (stdenv.isi686 || stdenv.isx86_64 || "aarch64-linux" == stdenv.hostPlatform.system)
+, threadSupport ? (stdenv.isi686 || stdenv.isx86_64 || "aarch64-linux" == stdenv.hostPlatform.system || "aarch64-darwin" == stdenv.hostPlatform.system)
 , disableImmobileSpace ? false
   # Meant for sbcl used for creating binaries portable to non-NixOS via save-lisp-and-die.
   # Note that the created binaries still need `patchelf --set-interpreter ...`
@@ -79,7 +79,7 @@ stdenv.mkDerivation rec {
                   lib.concatStringsSep " "
                     (builtins.map (x: "--with-${x}") enableFeatures ++
                      builtins.map (x: "--without-${x}") disableFeatures)
-                }
+                } ${if stdenv.hostPlatform.system == "aarch64-darwin" then "--arch=arm64" else ""}
     (cd doc/manual ; make info)
 
     runHook postBuild