Testvecabi fails to build on some x86 arch with `-march=native`

[blapie]

It was pointed out in #476 that x86 build of testvecabi was failing due to a mismatch in CPU features.

https://github.com/rivosinc/sleef/actions/runs/6753516221/job/18360067282

This could be lifted by removing the -march=native option used to compile testvecabi, that was clashing with the -mavx512f option used to compile routines.

Should we re-enable this feature and fix issue with ABI uncovered by -march=native?