Only set cli11 folder property on CMake 3.19 and higher

[jherico]

Description

Don't attempt to change the CLI11 target FOLDER property unless on CMake 3.19 and higher. Per this comment it's apparently problematic on older versions of CMake.

General Checklist:

Please ensure the following points are checked:

No code or project setting changes. This is purely CMake meta-project information.

• This PR describes the scope and expected impact of the changes I am making

Note: The Samples CI runs a number of checks including:

• I have updated the header Copyright to reflect the current year (CI build will fail if Copyright is out of date)
• My changes build on Windows, Linux, macOS and Android. Otherwise I have documented any exceptions

[SaschaWillems]

Thank you very much for this PR 👍🏻