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

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

Signed-off-by: Dan Trifan <jimsth@gmail.com>
Test increasing LTO compression to the max level (9)

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

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