[PATCH] um: kunit: resolve missing prototypes warning

[Gabriele Monaco]

First of all, thanks for the quick reply

> I get that you have this on kunit on ARCH=um, but that makes it
> neither
> a kunit nor a um patch :)

Well, yes I wasn't entirely sure how to put it, sure people from
UM/KUnit know what this is about, but I agree perhaps the patch title
can be a bit misleading.

> Arnd had originally wanted to fix this another way, but that got
> dropped. I don't know if this fix is right, though I can see that it
> works. I have the same workaround in my tree, but I'm really not
> convinced that it doesn't have side-effects on other architectures.

I thought about doing it differently, perhaps using an additional
header file or even re-arranging the macro dependency, this seemed to
me the easiest and perhaps less risky for other architectures, but I
get the concerns.

I could perform some further analyses building it for multiple targets
(besides _it builds_ I mean), if you have anything specific in mind.

Gabriele