derived-secrets: fix broken encoding

hosts/modules/derived-secrets/default.nix

@@ -40,6 +40,7 @@ in
       generated.command = [
         "${hash-path-with-salt}/bin/hash-path-with-salt"
         path
+        c.encoding
       ];
       generated.acl.mode = "0600";
     }) cfg;

hosts/modules/derived-secrets/hash-path-with-salt

@@ -1,9 +1,11 @@
 #!/usr/bin/env nix-shell
 #!nix-shell -i bash
-echo "$1" | cat /dev/stdin /etc/ssh/host_keys/ssh_host_ed25519_key \
+file="$1"
+enc="$2"
+echo "$file" | cat /dev/stdin /etc/ssh/host_keys/ssh_host_ed25519_key \
   | sha512sum \
   | cut -c 1-${toString (c.len * 2)} \
   | tr a-z A-Z \
   | basenc -d --base16 \
-  | basenc --${c.encoding} \
-  > "$1"
+  | basenc "--$enc" \
+  > "$file"