[RFC][top-level] Add configure test-case

[Joseph Myers]

On Mon, 7 Nov 2022, Alan Modra via Binutils wrote:

> a) that top-level binutils/gdb patches don't get applied to the gcc
>    git repository in a timely manner, or

If a toplevel patch is approved for either repository, I think you should 
treat it as approved for the other one without needing separate review.

-- 
Joseph S. Myers
joseph@codesourcery.com