[lld] [lld][ELF] Allow `.data.rel.ro.unlikely` to be RELRO (PR #148920)

[Fangrui Song via llvm-commits]

================
@@ -0,0 +1,89 @@
+# REQUIRES: x86
+
+# RUN: rm -rf %t && split-file %s %t && cd %t
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux input.s -o a.o
+
+# RUN: ld.lld -z keep-data-section-prefix -T linker-script.lds a.o -o a.out
+# RUN: llvm-readelf -l a.out | FileCheck --check-prefixes=SEG,LS %s
+# RUN: llvm-readelf -S a.out | FileCheck %s --check-prefix=CHECK-LS
+
+# RUN: ld.lld -z keep-data-section-prefix a.o -o b.out
+# RUN: llvm-readelf -l b.out | FileCheck --check-prefixes=SEG,PRE %s
+# RUN: llvm-readelf -S b.out | FileCheck %s --check-prefix=CHECK-PRE
+
+# RUN: ld.lld a.o -o c.out
+# RUN: llvm-readelf -l c.out | FileCheck --check-prefixes=SEG,PRE %s
+# RUN: llvm-readelf -S c.out | FileCheck %s --check-prefix=CHECK-PRE
+
+# RUN: not ld.lld -T linker-script.lds a.o -o d.out 2>&1 | FileCheck %s
----------------
MaskRay wrote:

omit `-o ` for `not ld.lld`, since lld will not create the output file  anyway

https://github.com/llvm/llvm-project/pull/148920