contrib: soxr: fix neon detection for aarch64 hosts

When soxr is used on Darwin arm64 plarforms, the expected resampler engine to be used is cr32s, but cr32 was used instead.
The simd detection module for cmake configuration was only checking for "arm" prefixed hosts.
Considering we use "aarch64" for arm64 hosts in contribs, these changes are an attempt to fix this.