reproduce (this is a W=1 build):
        # https://github.com/rgushchin/linux/commit/f811653ff6f0f0c1e8b85e1fe6a68724d2b707c6
        git remote add rgushchin https://github.com/rgushchin/linux.git
        git fetch --no-tags rgushchin bpfoom.2.2
        git checkout f811653ff6f0f0c1e8b85e1fe6a68724d2b707c6
        # apt-get install sparse
        # sparse version: v0.6.4-71-g610d841d

        # 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=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash