enhance(main/util-linux): build libmount and {lib,}fdisk

Put libmount library in subpackage libmount, mount utilities in
subpackage mount-utils, libfdisk in subpackage libfdisk, and fdisk
utilities in subpackage fdisk.

On my aarch64 device, /system/bin/mount is unable to handle logical
volumes (tries to access the non-existing /etc/fstab and errors), so
lets add our own libmount package.

Enabling libmount also enables the lsblk utility, which we put in
blk-utils.

packages/util-linux/build.sh

@@ -59,4 +59,3 @@ termux_step_pre_configure() {
 		TERMUX_PKG_EXTRA_CONFIGURE_ARGS+=" ac_cv_func_prlimit=yes"
 	fi
 }
-