[heads-up] disabling "../configure --disable-bootstrap && make bootstrap"

[Richard Kenner]

> You won't be able to do that any more.  We've been saying that since
> the first top level bootstrap rules went in, every time the subject
> came up - this really shouldn't be a surprise.

No, what's been said is that there will be a MODE in which that can't
be done, but it was always claimed that no capability would be lost with
these changes.  Now we're seeing a loss, and it's a very significant one.

> Libgcc will no longer be configured by the gcc subdirectory's makefile.
> Therefore there will be no startfiles or libgcc for the new compiler to
> use.

Sure there is: the one the last iteration used!  Obviously, if you're only
bootstrapping the compiler, you're going to leave everything else unchanged.