sysutils/elfx86exts: new port

Disassemble a binary and print out which instruction set extensions it uses.

Despite the utterly misleading name, this tool supports ELF and MachO
binaries, and perhaps other formats as well, and has preliminary
support for ARM64 as well as X86/64.

PR: 277939
Author: Jamie Landeg-Jones <jamie@catflap.org>
Date: Mon May 20 08:52:03 2024 +0200