[llvm] [NFCI][Globals] In GlobalObjects::setSectionPrefix, do conditional update if existing prefix is not equivalent to the new one. Returns whether prefix changed. (PR #158460)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-debian-cpp20` running on `clang-debian-cpp20` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/108/builds/17751

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/X86/memcmp-pgso.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llc < /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll -mtriple=x86_64-unknown-unknown | /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/FileCheck /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll --check-prefixes=X64,X64-SSE2
# executed command: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llc -mtriple=x86_64-unknown-unknown
# executed command: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/FileCheck /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll --check-prefixes=X64,X64-SSE2
# .---command stderr------------
# | /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll:75:13: error: X64-NEXT: expected string not found in input
# | ; X64-NEXT: jne .LBB4_3
# |             ^
# | <stdin>:66:15: note: scanning from here
# |  cmpw %cx, %ax
# |               ^
# | <stdin>:67:2: note: possible intended match here
# |  jne .LBB4_1
# |  ^
# | /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll:153:13: error: X64-NEXT: expected string not found in input
# | ; X64-NEXT: jne .LBB9_3
# |             ^
# | <stdin>:146:17: note: scanning from here
# |  cmpl %ecx, %eax
# |                 ^
# | <stdin>:147:2: note: possible intended match here
# |  jne .LBB9_1
# |  ^
# | /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll:247:13: error: X64-NEXT: expected string not found in input
# | ; X64-NEXT: jne .LBB15_2
# |             ^
# | <stdin>:242:17: note: scanning from here
# |  cmpq %rdx, %rcx
# |                 ^
# | <stdin>:243:2: note: possible intended match here
# |  jne .LBB15_1
# |  ^
# | /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll:277:13: error: X64-NEXT: expected string not found in input
# | ; X64-NEXT: jne .LBB16_2
# |             ^
# | <stdin>:272:17: note: scanning from here
# |  cmpq %rdx, %rcx
# |                 ^
# | <stdin>:273:2: note: possible intended match here
# |  jne .LBB16_1
# |  ^
# | 
# | Input file: <stdin>
# | Check file: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/CodeGen/X86/memcmp-pgso.ll
# | 
...

```

</details>

https://github.com/llvm/llvm-project/pull/158460