[PATCH] x86-64: Require BMI2 for strchr-avx2.S

[Florian Weimer]

* H. J. Lu via Libc-alpha:

> Since strchr-avx2.S updated by
>
> commit 1f745ecc2109890886b161d4791e1406fdfc29b8
> Author: noah <goldstein.w.n@gmail.com>
> Date:   Wed Feb 3 00:38:59 2021 -0500
>
>     x86-64: Refactor and improve performance of strchr-avx2.S
>
> uses sarx:
>
> c4 e2 72 f7 c0       	sarx   %ecx,%eax,%eax
>
> for strchr-avx2 family functions, require BMI2 in ifunc-impl-list.c and
> ifunc-avx2.h.

Seems reasonable, thanks.

Florian