arm64: Tweaks to compile with FORTIFY_SOURCE

[dsl]

Summary

I had to patch those files in order to build world:

$ nice make -s -j16 buildworld TARGET="arm64"

with:

$ cat /etc/src-env.conf 
FORTIFY_SOURCE=2
$ cat /etc/src.conf 
WITH_RETPOLINE=yes
WITH_KERNEL_RETPOLINE=yes
WITH_BIND_NOW=yes
OPT_INIT_ALL=zero

I'm pretty sure that I didn't have to patch contributed code directly. Moreover, building world for amd64 went well. Any idea how to fix buildworld for arm64 with those parameters above?

Test Plan

N/A

[kevans]

I'll provide some feedback here within a few hours, but yeah, we'll want to do this a little bit differently.... Can you extract where you ran into the ZFS problem at specifically, please?

[dsl]

World for arm64 can be built with 905541dd6ba4 without my changes. I'll abandon this review then.