security/nettle: Fix build of assembly code on aarch64
PR: 264946
Reported by: diizzy
Tested by: diizzy (RockPro64 with GnuTLS on 13.1-RELEASE)
Obtained from: https://git.lysator.liu.se/nettle/nettle/-/commit/d4c7597e4236f746434c9a1a24f6191f7ff870cd