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 <christian.ehrhardt@canonical.com>
Acked-by: Luca Boccassi <bluca@debian.org>