nixos/console: fix optimizedKeymap derivation isUnicode condition

The `optimizedKeymap` derivation was introduced in commit c9276c1b52
(2019) to pre-compile text keymaps into binary format for faster loading
during early boot (initrd).

The `-u` flag of `loadkeys` command enables Unicode mode, allowing the
keymap to contain Unicode keysyms (like `leftquote`,
`left_double_quotation_mark`). Without `-u` only non-Unicode keysyms are
supported (suitable for `ISO-8859-*` character sets).

When `console.useXkbConfig = true`, the keymap is generated by `ckbcomp`
which always produces Unicode keysyms, regardless of the local charset.
Hence this commit is a followup to #408307, and fixes #445666 for sure
while probably also fixing #411374 .

nixos/modules/config/console.nix

@@ -9,7 +9,7 @@ let
 
   makeColor = i: lib.concatMapStringsSep "," (x: "0x" + lib.substring (2 * i) 2 x);
 
-  isUnicode = lib.hasSuffix "UTF-8" (lib.toUpper config.i18n.defaultLocale);
+  isUnicode = config.i18n.defaultCharset == "UTF-8" || cfg.useXkbConfig;
 
   optimizedKeymap =
     pkgs.runCommand "keymap"

nixos/tests/console-xkb-and-i18n.nix

@@ -4,8 +4,8 @@
   meta.maintainers = with lib.maintainers; [ doronbehar ];
 
   nodes = {
-    # Nothing to run on this node, a bug (TODO: where?) is causing a builder of
-    # the configuration to fail. See:
+    # Nothing to run on this node. Only verify that this configuration doesn't
+    # produce the bugs described here:
     #
     # - https://github.com/NixOS/nixpkgs/issues/445666
     # - https://github.com/NixOS/nixpkgs/issues/411374