nixfmt-rfc-style

There is nothing in this commit except for the changes made by
nix-shell -p nixfmt-rfc-style --run "nixfmt ."

If this has mucked up your open branches then sorry about that. You
can probably nixfmt them to match before merging

tests/jffs2/configuration.nix

@@ -1,7 +1,8 @@
-{ config, pkgs, ... } :
+{ config, pkgs, ... }:
 let
   inherit (pkgs.pseudofile) dir;
-in {
+in
+{
   imports = [
     ../../vanilla-configuration.nix
     ../../modules/outputs/squashfs.nix