Add Optimize build flags

Signed-off-by: Seongmin Park <r_data@naver.com>
Use ccache so that it recompiles faster after a make clean.

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>

Conflicts:

	Makefile

Signed-off-by: Seongmin Park <r_data@naver.com>
Makefile: Add CCache in CROSS_COMPILE

Signed-off-by: Seongmin Park <r_data@naver.com>

Conflicts:

	Makefile
Makefile: Add -mfpu=neon-vfpv4 and CFLAGS

Signed-off-by: Seongmin Park <r_data@naver.com>
Makefile: Add -O2 options

Signed-off-by: Seongmin Park <r_data@naver.com>
Makefile: Add Optimize O3 level option

Signed-off-by: Seongmin Park <r_data@naver.com>
Makefile: fix typo;;

Signed-off-by: Seongmin Park <r_data@naver.com>