Allow an impure absolute stylix.image path for end-user convenience by
relaxing the guarantees established in commits ca1bc329e9
("stylix/palette: coerce derivations to store paths") and 61c9f4dd14
("treewide: remove redundant stylix.image escaping and string
coercion").
When stylix.image cannot be copied to the store, it is not guaranteed to
be a stringified store path with a valid string context and no special
characters, resulting in UB.
Link: https://github.com/nix-community/stylix/pull/2150
Reviewed-by: Matt Sturgeon <matt@sturgeon.me.uk>
Reviewed-by: 0xda157 <da157@voidq.com>
05e53b52b6