Only discard space for pc-relative relocs symbols

Only discard space for pc-relative relocs symbols

When building PIE, we should only discard space for pc-relative relocs
symbols which turn out to need copy relocs.

bfd/

	PR ld/17827
	* elf64-x86-64.c (elf_x86_64_allocate_dynrelocs): For PIE,
	only discard space for pc-relative relocs symbols which turn
	out to need copy relocs.

ld/testsuite/

	PR ld/17827
	* ld-x86-64/pr17689.out: Updated.
	* ld-x86-64/pr17689b.S: Likewise.

	* ld-x86-64/pr17827.rd: New file.

	* ld-x86-64/x86-64.exp: Run PR ld/17827 test.