[CMake] How to easily join list elements in a string?

[Marcel Loose]

Hi all,

I was wondering, does the opposite of separate_arguments() exist?
In other words, is there an easy way to join the elements of a list into
a space-separated string?

Of course I can write a macro to do the trick, but I have the feeling
that I'm overlooking something, because it sounds too trivial.

Best regards,
Marcel Loose.