opts-common.c (decode_cmdline_option): Print empty string argument as "" in decoded->orig_option_with_args_text.

	* opts-common.c (decode_cmdline_option): Print empty string
	argument as "" in decoded->orig_option_with_args_text.
	* gcc.c (execute): Print empty string argument as ""
	in the verbose output.
	(do_spec_1): Keep empty string argument.

	testsuite/
	* gcc.dg/cpp/include7.c: New test.

From-SVN: r170426