Skip an archive element if not added by linker

During archive rescan to resolve symbol references for files added by
LTO, linker add_archive_element callback is called to check if an
archive element should added.  After all IR symbols have been claimed,
linker won't claim new IR symbols and shouldn't add the LTO archive
element.  This patch updates linker add_archive_element callback to
return FALSE when seeing an LTO archive element during rescan and
changes ELF linker to skip such archive element.

bfd/

	PR ld/20103
	* cofflink.c (coff_link_check_archive_element): Return TRUE if
	linker add_archive_element callback returns FALSE.
	* ecoff.c (ecoff_link_check_archive_element): Likewise.
	* elf64-ia64-vms.c (elf64_vms_link_add_archive_symbols): Skip
	archive element if linker add_archive_element callback returns
	FALSE.
	* elflink.c (elf_link_add_archive_symbols): Likewise.
	* pdp11.c (aout_link_check_ar_symbols): Likewise.
	* vms-alpha.c (alpha_vms_link_add_archive_symbols): Likewise.
	* xcofflink.c (xcoff_link_check_dynamic_ar_symbols): Likewise.
	(xcoff_link_check_ar_symbols): Likewise.

ld/

	PR ld/20103
	* ldmain.c (add_archive_element): Don't claim new IR symbols
	after all IR symbols have been claimed.
	* plugin.c (plugin_call_claim_file): Remove no_more_claiming
	check.
	* testsuite/ld-plugin/lto.exp (pr20103): New proc.
	Run PR ld/20103 tests.
	* testsuite/ld-plugin/pr20103a.c: New file.
	* testsuite/ld-plugin/pr20103b.c: Likewise.
	* testsuite/ld-plugin/pr20103c.c: Likewise.