devel/ocaml-lacaml: remove -march=native

An existing site patch tried to remove -march=native, but this failed
to be effective. Rework the patch so -march=native is never passed.

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

(cherry picked from commit 25bfd8147fec94070189e30b8a2ec71227d99974)