Make the -O2 flag part of the extra compiler args
Make the -O2 flag part of the extra compiler args

This way it can be easily overridden for debug builds.

Signed-off-by: Maxime Petazzoni <d85b6a1285e9bda1f090e0e96b2c20e3f562641e@turn.com>

opennvm/nvmkv-java,opennvm/nvmkv-java,opennvm/nvmkv-java