zfs: unbreak aarch64 build with non-gcc compilers

Vendor did not backport this fix into zfs-2.2-release yet.

OpenZFS PR: #16103 35bf25848 Fix: FreeBSD Arm64 does not build currently
Approved by: re (cperciva)

(cherry picked from commit b9dee1dca2d74e12e867fd29d2d584fc385078eb)
(cherry picked from commit 7e10c2d27a538aa3f5afcafe48801a9316e30027)