Fix slowdown in ld -r for most common case of out-of-order relocs

Fix slowdown in ld -r for most common case of out-of-order relocs

I chose insertion sort since relocs are mostly sorted, but there is a
common case we can handle better;  A run of relocs put out of order
due to not linking input files in order.

	PR 18867
	* elflink.c (elf_link_adjust_relocs): Modify insertion sort to
	insert a run.  Return status in case of malloc failure.
	Adjust callers.