CMake: Check for PERL's List::MoreUtils

[JohannesLorenz]

This fixes a very annoying compile warning which always comes on a fresh Linux where List::MoreUtils is yet missing. This warning should already come at CMake time, so this is what this PR does.

[anytizer]

perl -MCPAN -e install List::MoreUtils was really necessary.

[Veratil]

Could we make CMake install it if it's missing? 😁

[JohannesLorenz]

perl -MCPAN -e install List::MoreUtils was really necessary.

Sorry, what do you mean?

[JohannesLorenz]

Could we make CMake install it if it's missing? 😁

I think in most cases, at least on Linux, users want to install such module via the package manager, which requires privileges.

Best thing we could do is tell users how to do it, though this differs a lot between the distros, and might even differ between versions.

[anytizer]

perl -MCPAN -e install List::MoreUtils was really necessary.

Sorry, what do you mean?

After seeing your PR, I looked how I had resolved the case in my computer.
That command installed MoreUtils in Ubuntu. It was a requirement even before cmake could complete.