elements/bootstrap/gcc-arch-opts.yml: tune for POWER8 and up
This selects a minimum supported CPU level of POWER8 (the first CPU with ppc64le support) and tunes for POWER8.
This is the default in, for example, fedora: https://src.fedoraproject.org/rpms/redhat-rpm-config/blob/master/f/buildflags.md
Edited by Javier Jardón