reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        git remote add chrome-os https://chromium.googlesource.com/chromiumos/third_party/kernel
        git fetch --no-tags chrome-os chromeos-5.15
        git checkout 3c22f4cfab67e9e5d8cf9c56f5ed6906ee5533eb
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=i386 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=i386 SHELL=/bin/bash