Current ppc stage 3 tarball (stage3-ppc-openrc-20240516T033339Z) tells the user "Please consult /usr/share/portage/config/make.conf.example for a more detailed example." in /etc/portage/make.conf. This make.conf.example contains outdated information though regarding no longer used GCC versions and CFLAGS. It suggests the user e.g. to set "-fno-strict-aliasing" in CFLAGS. This contradicts current Gentoos' Safe CFLAGS recommendations: https://wiki.gentoo.org/wiki/Safe_CFLAGS#PowerPC_.2F_PowerPC_64 ppc64 stages are ok in that regard and in sync with Gentoos' Safe CFLAGS.
make.conf.example is installed by sys-apps/portage.