While there is a function nano_makefs() that already takes care of this
issue, we are not yet ready to consume it.
Just add the time stamp and FFS options to makefs. This is done
primarily to use UFS2 (UFS version 2). If the user needs further
customization, the variable NANO_MAKEFS can be overridden. Timestamping
takes care of making the images bit-for-bit identical.