[Bug other/91879] --with-build-time-tools doesn't work as expected

[stsp at users dot sourceforge.net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91879

--- Comment #31 from Stas Sergeev <stsp at users dot sourceforge.net> ---
(In reply to joseph@codesourcery.com from comment #29) 
> A common way of doing that is to make $host and $build textually different 
> (after passing through config.sub) while still logically the same.  E.g. 
> x86_64-pc-linux-gnu versus x86_64-unknown-linux-gnu.

And being a trick, it appears non-trivial.
I would want the CPU part to be the same.
I.e.
x86_64-pc-linux-gnu --> x86_64-unknown-linux-gnu
i686-pc-linux-gnu --> i686-unknown-linux-gnu

The problem here is that I can't hard-code $host
to any of that value. It must be evaluated from
$build somehow. Do you have a trick also for that?
Probing manually for uname before configure?
Or maybe its time to add a new option after all? :)