Handle weak alias for PIE with copy reloc

When there is a weak symbol with a real definition, the processor
independent code will have arranged for us to see the real definition
first.  We need to copy the needs_copy bit from the real definition and
check it when allowing copy reloc in PIE.

bfd/

	PR ld/17689
	* elf64-x86-64.c (elf_x86_64_link_hash_entry): Add needs_copy.
	Change has_bnd_reloc to bit field.
	(elf_x86_64_link_hash_newfunc): Initialize needs_copy and
	has_bnd_reloc to 0.
	(elf_x86_64_check_relocs): Set has_bnd_reloc to 1 instead
	of TRUE.
	(elf_x86_64_adjust_dynamic_symbol): Copy needs_copy from the
	real definition to a weak symbol.
	(elf_x86_64_allocate_dynrelocs): Also check needs_copy of a
	weak symbol for PIE when discarding space for relocs against
	symbols which turn out to need copy relocs.
	(elf_x86_64_relocate_section): Also check needs_copy of a
	weak symbol for PIE with copy reloc.

ld/testsuite/

	PR ld/17689
	* ld-x86-64/pr17689.out: New file.
	* ld-x86-64/pr17689.rd: Likewise.
	* ld-x86-64/pr17689a.c: Likewise.
	* ld-x86-64/pr17689b.S: Likewise.

	* ld-x86-64/x86-64.exp: Run PR ld/17689 tests.
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