Since "-z now" replaces PLT with GOT PLT, we should also check GOT PLT
for R_X86_64_PLTOFF64 relocation.
bfd/
PR ld/20800
* elf64-x86-64.c (elf_x86_64_relocate_section): Also check
plt_got.offset for R_X86_64_PLTOFF64.
ld/
PR ld/20800
* testsuite/ld-x86-64/pr20800a.S: New file.
* testsuite/ld-x86-64/pr20800b.S: Likewise.
* testsuite/ld-x86-64/x86-64.exp: Run PR ld/20800 test.