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

[Alan Modra]

On Thu, Oct 20, 2022 at 05:10:28PM +0200, Tom de Vries via Binutils wrote:
> Hi,
> 
> As reported in reopened PR18632, recent commit 228cf97dd3c ("Merge configure.ac
> from gcc project") dropped commit 69961a84c9b ("Don't build
> readline/libreadline.a, when --with-system-readline is supplied"), due to the
> patch only being applied to binutils-gdb repo, and not to gcc repo.

Sorry about that.

> I wondered if I could write a test-case that would regress because of this,
> such that we at least don't silently regress.
> 
> I came up with a test-case named toplevel.exp, that can be run like this:

While I applaud anything that helps stop Alan making silly mistakes,
the real problem is either
a) that top-level binutils/gdb patches don't get applied to the gcc
   git repository in a timely manner, or
b) that we try to keep them in sync.

Maybe we should just give up on (b)?

-- 
Alan Modra
Australia Development Lab, IBM