cc: Enable global O3

At level 3 optimization loop vectorization gets enabled which can lead
to significant speedups when processing big chunks of data. Rather than
enabling O3 one by one let's enable it globally as this flag is
completely safe nowadays.

Signed-off-by: Andrzej Perczak <linux@andrzejperczak.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>