treewide: Escape backslash in strings properly

"\." is apparently the same as "." wheras the correct one is "\\."

pkgs/development/idris-modules/default.nix

@@ -26,7 +26,7 @@
     };
 
     files = builtins.filter (n: n != "default") (pkgs.lib.mapAttrsToList (name: type: let
-      m = builtins.match "(.*)\.nix" name;
+      m = builtins.match "(.*)\\.nix" name;
     in if m == null then "default" else builtins.head m) (builtins.readDir ./.));
   in (builtins.listToAttrs (map (name: {
     inherit name;