PR gold/10708

	PR gold/10708
	* copy-relocs.cc (Copy_relocs::emit_copy_reloc): Hold a lock on the
	object when reading from the file.
	* gold.cc (queue_middle_tasks): Hold a lock on the object when doing
	second layout pass.
	* icf.cc (preprocess_for_unique_sections): Hold a lock on the object
	when reading section contents.
	(get_section_contents): Likewise.
	(icf::find_identical_sections): Likewise.
	* mapfile.cc (Mapfile::print_discarded_sections): Hold a lock on the
	object when reading from the file.
	* plugin.cc (Plugin_manager::layout_deferred_objects): Hold a lock on
	the object when doing deferred section layout.