reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/broonie/ci.git/commit/?id=c8ad2f2d94132360954e4d5dbb87a87e9a58d9c3
        git remote add broonie-ci https://git.kernel.org/pub/scm/linux/kernel/git/broonie/ci.git
        git fetch --no-tags broonie-ci regulator-mp8859
        git checkout c8ad2f2d94132360954e4d5dbb87a87e9a58d9c3
        # 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/regulator/