[Android] Build with -O2

[Edward Wang]

On 13-01-11 05:18 AM, git at videolan.org (Rafaël Carré) <git at videolan.org 
(Rafaël Carré)> wrote:
> +EXTRA_CFLAGS="${EXTRA_CFLAGS} -O2"
> +
Maybe we should add -O2 only to release builds to aid in debugging?

Regards,
         Edward Wang