options: Make --help= see overridden values

options: Make --help= see overridden values

Options "-Q --help=params" don't show the final values after
target option overriding, instead it emits the default values
in params.opt (without any explicit param settings).

This patch makes it see overridden values.

gcc/ChangeLog:

	* opts-global.c (decode_options): Call target_option_override_hook
	before it prints for --help=*.