Any blanket advice like that should be taken with a grain of salt.
Every application+target environment combination is unique, so to get
the best results, test and measure.
I have to put something in the makefile. I switched
it to Os from O3 based on my observations here. I also
tested switching from O3 to Os on another program and
found the same results -- equal run time results and
better build times. So I decided to make Os the default
for now. From reading about Os, it uses most of the