PR30155, ld segfault in _bfd_nearby_section

The segfault was a symptom of messing with the absolute section next
field, confusing bfd_section_removed_from_list in linker.c:fix_syms.
That's not all that was going wrong.  The INSERT list of output
sections was being inserted into itself, ie. lost from the main
list of linker statements.

	PR 30155
	* ldlang.c (process_insert_statements): Handle pathological
	case of the insert script being inserted before the first
	output section statement in the default script.
	(output_prev_sec_find): Don't test section owner here.
	(insert_os_after): Change parameter to a list union pointer.
	(lang_insert_orphan): Test section owner here and adjust
	insert_os_after call.

(cherry picked from commit 18e7a658)