bug#48228: json-serialize should signal error when dll is not found [MS Windows]

[Eli Zaretskii]

> From: Nikolay Kudryavtsev <nikolay.kudryavtsev@gmail.com>
> Cc: dgutov@yandex.ru, rpluim@gmail.com, p.stephani2@gmail.com,
>  48228@debbugs.gnu.org
> Date: Thu, 6 May 2021 19:29:20 +0300
> 
> On the other hand, it is quite possible that X years down the line the 
> bundled miniGMP would get out of step with the main GMP and you'd have a 
> reason to use one instead of the other. And having a run time check 
> would help.

If that happens, we will indeed need to think about a predicate to
test that.  But for now it would be superfluous.