reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git/commit/?id=6ce042f025bd4c46f5d2fd37a048a516433b0b3d
        git remote add linusw-pinctrl https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git
        git fetch --no-tags linusw-pinctrl ib-mux-pinctrl
        git checkout 6ce042f025bd4c46f5d2fd37a048a516433b0b3d

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