PR 10979

	* script.cc (read_input_script): If we see a new SECTIONS clause,
	and we have added an input section, give an error.
	* layout.h (class Layout): Add have_added_input_section function.
	Add have_added_input_section_ field.
	* layout.cc (Layout::Layout): Initialize
	have_added_input_section_.
	(Layout::layout): Set have_added_input_section_.
	(Layout::layout_eh_frame): Likewise.