Run `byte-recompile-directory' on the dirs remaining on the command line.
Must be used only with `-batch', and kills Emacs on completion.
For example, invoke `emacs -batch -f batch-byte-recompile-directory .'.
Optional argument ARG is passed as second argument ARG to
`byte-recompile-directory'; see there for its possible values
and corresponding effects. (fn &optional ARG)