Add multiple inputs to configure_file()

[elmarco]

For command, it is useful to be able to express multiple input files,
just like custom_target().

WIP until tests are added, and probably some FeatureNew checks etc.

[xclaesse]

I think command can be an array with files in the command arguments. That doesn't work?

[nirbheek]

input: is useful when you want to tell meson to reconfigure if that file changes, so this sounds useful in case you're generating something using multiple input files.

[xclaesse]

I meant that if you have files in the command: [] kwarg, it will also add them into deps. But I guess there could be cases where you want to add deps that are not explicitly passed to the command line.

[elmarco]

ping (required by qemu port)

thanks

[xclaesse]

I totally forgot about this MR, and I ran into the same problem, so I re-made pretty much the same patch: #5895.

@elmarco I think my patch there is slightly better because it covers 2 related issues. I shamelessly copied your release snippet :)

[elmarco]

@xclaesse nm, that happens to me as well. Let's close and take your version if it's better.

[xclaesse]

Ok, thanks. Closing this now.