1. Android build
  - Download original android source code ( android-7.0.0_r1 ) from http://source.android.com
  - Untar opensource packages of F720_Nougat_Android.tar.gz into downloaded android source directory
       a) tar -xvzf F720_Nougat_Android.tar.gz
  - And, merge the source into the android source code
  - Run following scripts to build android
    a) source build/envsetup.sh
    b) lunch 1
    c) make -j4
  - When you compile the android source code, you have to add google original prebuilt source(toolchain) into the android directory.
  - After build, you can find output at out/target/product/generic

2. Kernel Build  
  - Uncompress using following command at the android directory
        a) F720_Nougat_Kernel.tar.gz

  - When you compile the kernel source code, you have to add google original prebuilt source(toolchain) into the android directory.
  - Run following scripts to build kernel
  
    a) cd kernel
    b)     
    	case F720L) make ARCH=arm ph1_lgu_kr-perf_defconfig
    	case F720S) make ARCH=arm ph1_skt_kr-perf_defconfig
    	case F720K) make ARCH=arm ph1_kt_kr-perf_defconfig    	    
    c) make ARCH=arm CROSS_COMPILE=../../prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9/bin/arm-linux-androideabi- -j4
	
	* "-j4" : The number, 4, is the number of multiple jobs to be invoked simultaneously. 
  - After build, you can find the build image(Image.gz) at arch/arm64/boot

