bacula: fix build on aarch64-darwin

pkgs/tools/backup/bacula/default.nix

···
     sha256 = "sha256-AZWgi81PV4rkqc4Nkff4ZzHGNNVrgQU0ci1yGyqe7Lc=";
   };
 
+  # libtool.m4 only matches macOS 10.*
+  postPatch = lib.optionalString (stdenv.isDarwin && stdenv.isAarch64) ''
+    substituteInPlace configure \
+      --replace "10.*)" "*)"
+  '';
+
   buildInputs = [ postgresql sqlite zlib ncurses openssl readline ]
     ++ lib.optionals stdenv.hostPlatform.isDarwin [
       CoreFoundation