reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/ulfh/linux-pm.git/commit/?id=df4e9ec1ed8604380fa4508300dd0e6d60ddf4f4
        git remote add ulfh-pm https://git.kernel.org/pub/scm/linux/kernel/git/ulfh/linux-pm.git
        git fetch --no-tags ulfh-pm next
        git checkout df4e9ec1ed8604380fa4508300dd0e6d60ddf4f4

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/pmdomain/mediatek/