reproduce (this is a W=1 build):
        git remote add android-common https://android.googlesource.com/kernel/common
        git fetch --no-tags android-common android-4.19-stable
        git checkout f64a8b79c0e85440319136ed928f22ed37481742
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/staging/android/ion/