reproduce (this is a W=1 build):
        # https://github.com/Freescale/linux-fslc/commit/853944c5181946f7b7d04330e610316b49aee2d6
        git remote add freescale-fslc https://github.com/Freescale/linux-fslc
        git fetch --no-tags freescale-fslc 6.6-2.1.x-imx
        git checkout 853944c5181946f7b7d04330e610316b49aee2d6
        # 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/regulator/