reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git/commit/?id=e5d1202b6b1efa2a533564e21476dadb1b838f6b
        git remote add lee-mfd https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git
        git fetch --no-tags lee-mfd for-mfd-next
        git checkout e5d1202b6b1efa2a533564e21476dadb1b838f6b
        # 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/mfd/