libc/amd64: Disable ASAN for amd64_archlevel.c

The code in this file runs before the sanitizer can initialize its
shadow map.

Fixes: ad2fac552c3f ("lib/libc/amd64: add archlevel-based simd dispatch framework")

(cherry picked from commit 4dedcb1bb54cbbe8043c79ad733f966b6ffc6972)