reproduce (this is a W=1 build):
        git remote add android-common https://android.googlesource.com/kernel/common
        git fetch --no-tags android-common android17-6.18-kminext
        git checkout d35ca2f642726a2c8a85c5b864fd05f59f3965af
        # apt-get install llvm-dev

        # save the config file
        make W=1 ARCH=i386 olddefconfig
        make W=1 ARCH=i386 
        make W=1 headers_install
        make W=1 -C tools/testing/selftests