Add CPU_FLAGS_*:
================
*This program will add ISA extensions to your USE/Make flags.

1. Get program:
emerge --ask app-portage/cpuid2cpuflags

2. View your CPU Flags (if wanted):
cpuid2cpuflags

3. Add CPU flags to portage:
echo "*/* $(cpuid2cpuflags)" > /etc/portage/package.use/00cpu-flags

Source: https://wiki.gentoo.org/wiki/Handbook:PPC64/Installation/Base
Date: mid 2022 - late 2023