botan: Broken on aarch64

https://nix-cache.s3.amazonaws.com/log/2vjsb2fs5z9nkr4h4sjwvgy0vflbq4hg-botan-1.10.15.drv

pkgs/development/libraries/botan/generic.nix

@@ -45,7 +45,7 @@ stdenv.mkDerivation rec {
     inherit version;
     description = "Cryptographic algorithms library";
     maintainers = with maintainers; [ raskin ];
-    platforms = platforms.unix;
+    platforms = ["x86_64-linux" "i686-linux" "x86_64-darwin"];
     license = licenses.bsd2;
   };
   passthru.updateInfo.downloadPage = "http://files.randombit.net/botan/";