run: create -F option to run base64 encoded command after busybox init

Fix ./run -h which was showing the build help instead.

rootfs_overlay/etc/init.d/S98

@@ -1,7 +1,8 @@
 #!/bin/sh
 echo "hello S98"
 if [ -n "$lkmc_eval" ]; then
-  echo "$lkmc_eval"
   eval "$lkmc_eval"
+elif [ -n "$lkmc_eval_base64" ]; then
+  eval "$(printf "$lkmc_eval_base64" | base64 -d)"
 fi
 exit 0