Makefile: Add Config Variable Os - O2 - O3 for choice Compilation

Signed-off-by: Dan Trifan <jimsth@gmail.com>
Makefile optimizations

Signed-off-by: Dan Trifan <jimsth@gmail.com>
defconfig: enable graphite optimization, LTO and ffast_math

Signed-off-by: Dan Trifan <jimsth@gmail.com>