Compile android common branch with clang

RecenRecently I need to use clang to compile android kernel, it takes time to figure out the compiable one. Here's the step of my first success.

Step 1: Download ndk from the follwoing link and unzip it(Platform: ubuntu 18.04.1 LTS):

https://developer.android.com/ndk/downloads/

Step 2: Download android kernel source code from Google repo, this is the one I used:

git clone https://android.googlesource.com/kernel/common

Step 3:Pick a branch, I compile this one:

git checkout android-4.9

Step 4: Set up the environment variable, those are what I use:

export ARCH=arm64
export CROSS_COMPILE=/dir/to/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-

Step 5: Begin to compile:

make ranchu64_defconfig
make -j$(nproc --all) CC=dir/to/ndk/toolchains/llvm/prebuilt/linux-x86_64/bin/clang \
                      CLANG_TRIPLE=aarch64-linux-gnu-