1. Android build
  - Download original android source code (  android-9.0.0_r37 ) from http://source.android.com
  ( $repo init -u https://android.googlesource.com/platform/manifest -b android-9.0.0_r37
    $repo sync -cdq -j12 --no-tags
    $repo start  android-9.0.0_r37 --all
  )
	   
  - Then, 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) tar -xvzf *_Kernel_Pie.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/msm-3.18/ 
    b)mkdir -p ../../out
    c)make O=../../out ARCH=arm64 CROSS_COMPILE=../../prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/bin/aarch64-linux-android- falcon_global_com-perf_defconfig 
    d)make O=../../out ARCH=arm64 CROSS_COMPILE=../prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/bin/aarch64-linux-android- KCFLAGS=-mno-android -j4

  * "-j4" : The number, 4, is the number of multiple jobs to be invoked simultaneously. 
  - After build, you can find the build image(zImage) at out/arch/arm64/boot
 