ia64: add option to suppress warnings about A/B-step errata

[Zack Weinberg]

Andreas Schwab <schwab@suse.de> writes:

> Zack Weinberg <zack@codesourcery.com> writes:
>
>> Unfortunately the assembler does not ignore unrecognized -m options,
>> so there is a compatibility issue if I make GCC 3.4 (say) start
>> passing -mb-step along to the assembler
>
> That can be solved with a configure check in GCC.

I would prefer not to add another assembler-feature check for
something this trivial.

zw