armbian-next: rootfs: build rootfs from CLI, sans-BOARD, sans-FAMILY, etc -- rootfs are meant to be shared

- require ARCH/RELEASE for rootfs cli
- disallow BOARD/LINUXFAMILY/BOARDFAMILY being set for rootfs cli
- split `prep_conf_main_only_rootfs()` instead of `prep_conf_main_build_single()` for rootfs-only stuff
- run both conf and build without stdin for rootfs CLI (no interactive allowed)
- don't blindly set `ARCH=armhf` for no reason in main-config
- allow skipping family stuff in main-config, via `allow_no_family=yes` (used only in `prep_conf_main_only_rootfs()`)
- kill double loading of userpatches family, not needed/old code
- allow skipping kernel stuff via `skip_kernel=yes` in `config_pre_main()`  (used only in `prep_conf_main_only_rootfs()`)

lib/functions/rootfs/create-cache.sh

@@ -160,7 +160,7 @@ function create_new_rootfs_cache() {
 	declare cache_name=${ARCH}-${RELEASE}-${cache_type}-${packages_hash}-${ROOT_FS_CREATE_VERSION}.tar.zst
 	declare cache_fname=${SRC}/cache/rootfs/${cache_name}
 
-	display_alert "Creating new rootfs cache for" "${RELEASE} ${ROOT_FS_CREATE_VERSION}" "info"
+	display_alert "Creating new rootfs cache for" "'${RELEASE}' '${ARCH}' '${ROOT_FS_CREATE_VERSION}'" "info"
 
 	create_new_rootfs_cache_via_debootstrap # in rootfs-create.sh
 	create_new_rootfs_cache_tarball         # in rootfs-create.sh