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

[Zack Weinberg]

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

> This started out as a way to move the GNAT check to the toplevel.  It turns
> out that more than that is necessary in order to test $CC's capabilities in
> the toplevel configure script.  This tentative patch moves the logic to
> detect missing languages to the toplevel, and makes the gcc directory expect
> just --enable-languages=lang1,lang2 with all the prerequisites in place.

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.

zw