ci/build-freebsd: use march=native for QEMU hosted build

This is workaround to not emit instructions that are broken with current
version of QEMU used in CI job.

Fixes SIGBUS on valid code when executed in QEMU caused by issue with
CVTPS2PD instruction.

QEMU issue:
https://gitlab.com/qemu-project/qemu/-/issues/1377

QEMU fix:
https://gitlab.com/qemu-project/qemu/-/commit/abd41884c530aa025ada253bf1a5bd0c2b808219

Should be resolved after QEMU update to 8.2.0:
https://github.com/cross-platform-actions/action/issues/78