PLUGINS: avoid building explicit non-SIMD version of plugins
PLUGINS: avoid building explicit non-SIMD version of plugins

Our compiler setup now either supports SIMD (and auto-vectorization)
out of the box or not at all, so there's no point to build two variants.

Signed-off-by: Tim Janik <6ec6ff229c4e1c5bbd5933ee92e6c5832ff023bb@gnu.org>

GNOME/beast,tim-janik/beast,tim-janik/beast,swesterfeld/beast,GNOME/beast,swesterfeld/beast,GNOME/beast,tim-janik/beast,tim-janik/beast,swesterfeld/beast,swesterfeld/beast,swesterfeld/beast,tim-janik/beast,GNOME/beast,swesterfeld/beast,GNOME/beast,tim-janik/beast,GNOME/beast,GNOME/beast,swesterfeld/beast,tim-janik/beast