[RFC] Move --enable-languages logic to the toplevel

[Zack Weinberg]

Paolo Bonzini <paolo.bonzini@polimi.it> writes:

>> This patch looks plausible.  You should test the toplevel configure in
>> a binutils tree, to make sure it behaves sensibly when there is no gcc
>> subdirectory.
>
> Needless to say, it does not (it works, but passes a bogus
> --enable-languages=c option).  I will add a revised patch to the
> (already long) queue of patches waiting for the copyright assignment
> form to reach me. :-( In the meanwhile I created PR14131 and
> assigned it to me.

Understood.  In the meantime, I think it would be a good idea to
disable Ada by default on the mainline, so that people without an Ada
bootstrap compiler handy are not unexpectedly burnt by this problem.
Those who intend to build Ada can specify --enable-languages=ada.
Thoughts?

zw