Postpone print of --help=* option.

Postpone print of --help=* option.

2019-05-02  Martin Liska  <mliska@suse.cz>

	* gcc.c (process_command): Add dummy file only
	if n_infiles == 0.
	* opts-global.c (decode_options): Pass lang_mask.
	* opts.c (print_help): New function.
	(finish_options): Print --help if help_option_argument
	is set.
	(common_handle_option): Factor out content of OPT__help_
	into print_help.
	* opts.h (finish_options): Add new argument.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@270788 138bc75d-0d04-0410-961f-82ee72b054a4