ld: Improve thin archive member error message

Improve thin archive member error message with:

ld: libbar.a(bar.o): error opening thin archive member: No such file or directory

instead of

ld: libbar.a: error adding symbols: No such file or directory

	PR ld/28722
	* archive.c (_bfd_get_elt_at_filepos): Add a pointer argument
	for struct bfd_link_info.  Call linker callback when failing to
	open thin archive member.
	(_bfd_generic_get_elt_at_index): Pass NULL to
	_bfd_get_elt_at_filepos.
	(bfd_generic_openr_next_archived_file): Likewise.
	* coff-alpha.c (alpha_ecoff_get_elt_at_filepos): Add a pointer
	argument for struct bfd_link_info and pass it to
	_bfd_get_elt_at_filepos.
	(alpha_ecoff_openr_next_archived_file): Pass NULL to
	_bfd_get_elt_at_filepos.
	(alpha_ecoff_get_elt_at_index): Likewise.
	* coff-rs6000.c (_bfd_xcoff_openr_next_archived_file): Likewise.
	* ecoff.c (ecoff_link_add_archive_symbols): Pass info to
	backend->get_elt_at_filepos.
	* elflink.c (elf_link_is_defined_archive_symbol): info to
	_bfd_get_elt_at_filepos.
	* libbfd-in.h (_bfd_get_elt_at_filepos): Add a pointer argument
	for struct bfd_link_info.
	* libbfd.h: Regenerate.
	* libecoff.h (ecoff_backend_data): Add a pointer argument for
	struct bfd_link_info to get_elt_at_filepos.
	* linker.c (_bfd_generic_link_add_archive_symbols): Pass info to
	_bfd_get_elt_at_filepos.