lib.optional returns a singleton or an empty list. Therefore the
argument does not need to be wrapped in a list.
An alternative patch could have used lib.optionals but seems like no
more elements are going to be added to the optional list.
I know that "devinfo" output does not currently exist, but so does "devman".
It is mentioned in the nixpkgs manual, but no derivation in nixpkgs actually uses it.
