specify -- with-cpu when compiling the glibc

[Florian Weimer]

* 赵爱南 via Libc-help:

> Hello:
> I'm a glibc developer.Now our architecture needs to specify -- with-cpu when compiling  the glibc, and then there has a error:
>
>
> "The $submachine subspecies of $host_cpu is not supported." "$LINENO" 5

It looks like the configure logic expects a sysdeps directory named
$submachine.  It's not clear what you are trying to achieve by using
--with-cpu if there is no such sysdeps directory.  You can pass -march=
or -mcpu= flags directly as CC="gcc -march=…" etc.

Thanks,
Florian