Fix: FreeBSD Arm64 does not build currently

The define LD_VERSION isn't defined on FreeBSD Arm64 when OpenZFS is
build with the default compiler: clang.
I used only gcc for testing - my fault.

Fast fix as suggested by @mmatuska

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Martin Matuska <mm@FreeBSD.org>
Signed-off-by: Tino Reichardt <milky-zfs@mcmilk.de>
Closes #16103