Use stable sort for ld -r relocs

Use stable sort for ld -r relocs

A number of targets emit multiple relocs at a given r_offset, and
depend on those relocs staying in their original order.

	PR 18867
	* elflink.c (cmp_ext32l_r_offset, cmp_ext32b_r_offset): Delete.
	(cmp_ext64l_r_offset, cmp_ext64b_r_offset): Delete.
	(ext32l_r_offset, ext32b_r_offset, ext64l_r_offset, ext64b_r_offset):
	New functions.
	(elf_link_adjust_relocs): Use an insertion sort to sort relocs.