[ELF] Rename .bss.rel.ro to .data.rel.ro.bss for some Linker Scripts.

[ELF] Rename .bss.rel.ro to .data.rel.ro.bss for some Linker Scripts.

LLD uses .bss.rel.ro for read-only copy relocations whereas the ld.bfd and
gold linkers use .data.rel.ro. In some linker scripts including ld.bfd's
internal linker script, the relro sections are placed sequentially assuming
.data.rel.ro is used. LLD's use of .bss.rel.ro means that the copy
relocations get matched into the .bss section causing the relro sections to
be non-contiguous.

This change checks for a .data.rel.ro OutputSection when a linker script
with the SECTIONS command is used. The section will match in the
.data.rel.ro output section and will maintain contiguous relro.

Differential Revision: https://reviews.llvm.org/D40365

Fixes PR35265

llvm-svn: 318940