elf: Verify section size for mixed ordered/unordered inputs

When fixing up SHF_LINK_ORDER, issue a fatal error if the output section
size is increased.  Otherwise, bfd_set_section_contents will fail later
when attempting to write contents past the end of the output section.

	PR ld/26256
	PR ld/27160
	* elflink.c (elf_fixup_link_order): Verify that fixing up
	SHF_LINK_ORDER doesn't increase the output section size.