reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?id=ad9f759418050a355eb90ac010b8db05d4d6f23c
        git remote add rafael-pm https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git
        git fetch --no-tags rafael-pm acpi-rtc
        git checkout ad9f759418050a355eb90ac010b8db05d4d6f23c

        # 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