devel/rubygem-oj: fix build on armv7

Port uses NEON intrinsics only available on Aarch64.
Disable use of NEON on armv7 to fix the build.

Approved by: portmgr (build fix blanket)
MFH: 2025Q3

(cherry picked from commit bf27db51bb874e9f440eb430abef228dab412198)