biology/ncbi-blast+: only for aarch64, amd64

This port uses SIMD intrincis to compute CRC checksums.
It's probably easy to add a generic code path if desired.

Approved by: portmgr (build fix blanket)
MFH: 2026Q1
Sponsored by: Raptor Computing Systems, LLC

(cherry picked from commit c306479f2b4a4dd7c6d7b7c716574a25a0748986)