reproduce (this is a W=1 build):
        # https://github.com/awilliam/linux-vfio/commit/292e9ee22b0adad49c9a6f63708988e32c007da6
        git remote add awilliam-vfio https://github.com/awilliam/linux-vfio.git
        git fetch --no-tags awilliam-vfio next
        git checkout 292e9ee22b0adad49c9a6f63708988e32c007da6
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash