reproduce (this is a W=1 build):
        # https://github.com/ambarus/linux-0day/commit/b6d1b619a848f5a304ae59ed71a414058e8d3013
        git remote add ambarus https://github.com/ambarus/linux-0day
        git fetch --no-tags ambarus hyperbus
        git checkout b6d1b619a848f5a304ae59ed71a414058e8d3013
        # 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 drivers/mtd/hyperbus/