batch-byte-compile is an autoloaded compiled Lisp function in `bytecomp.el'.

(batch-byte-compile &optional NOFORCE)

Run `byte-compile-file' on the files remaining on the command line.
Use this from the command line, with `-batch';
it won't work in an interactive Emacs.
Each file is processed even if an error occurred previously.
For example, invoke "emacs -batch -f batch-byte-compile $emacs/ ~/*.el".
If NOFORCE is non-nil, don't recompile a file that seems to be
already up-to-date.