build: avoid non supported -march on ppc with meson
build: avoid non supported -march on ppc with meson

So far only if machine was "native" it did use the re-direction to
not set -march on ppc64 (where -march is not supported).
We have to use mcpu/mtune in any case on ppc for whatever someone using
the build system defines as machine.

Fixes: 54d609a13876 ("build: add ppc64 meson build")

Signed-off-by: Christian Ehrhardt <48da28e2c2cd455d60e19b14c46925e20a3c5d5b@canonical.com>
Acked-by: Luca Boccassi <020748dc039465edc3ee6f30c530b21164cdce27@debian.org>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk