zfs: Fix build with GCC 12.

Silence -Winfinite-recursion for ldo.c in lua and -Wstringop-overread
for nvpair.c.

Reviewed by: mm
Differential Revision: https://reviews.freebsd.org/D37631

(cherry picked from commit 2e08e4b75ea1080c224a33baf62199d893dc322d)