[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-armv7-global-isel` running on `linaro-clang-armv7-global-isel` while building `llvm` at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/39/builds/7898

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

```
Step 7 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'LLVM :: CodeGen/X86/memcmp-pgso-x32.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
/home/tcwg-buildbot/worker/clang-armv7-global-isel/stage1/bin/llc < /home/tcwg-buildbot/worker/clang-armv7-global-isel/llvm/llvm/test/CodeGen/X86/memcmp-pgso-x32.ll -mtriple=i686-unknown-unknown -mattr=cmov | /home/tcwg-buildbot/worker/clang-armv7-global-isel/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv7-global-isel/llvm/llvm/test/CodeGen/X86/memcmp-pgso-x32.ll --check-prefixes=X86,X86-NOSSE
# executed command: /home/tcwg-buildbot/worker/clang-armv7-global-isel/stage1/bin/llc -mtriple=i686-unknown-unknown -mattr=cmov
# executed command: /home/tcwg-buildbot/worker/clang-armv7-global-isel/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv7-global-isel/llvm/llvm/test/CodeGen/X86/memcmp-pgso-x32.ll --check-prefixes=X86,X86-NOSSE
# .---command stderr------------
# | /home/tcwg-buildbot/worker/clang-armv7-global-isel/llvm/llvm/test/CodeGen/X86/memcmp-pgso-x32.ll:83:13: error: X86-NEXT: expected string not found in input
# | ; X86-NEXT: jne .LBB4_3
# |             ^
# | <stdin>:75:15: note: scanning from here
# |  cmpw %si, %dx
# |               ^
# | <stdin>:76:2: note: possible intended match here
# |  jne .LBB4_1
# |  ^
# | /home/tcwg-buildbot/worker/clang-armv7-global-isel/llvm/llvm/test/CodeGen/X86/memcmp-pgso-x32.ll:173:13: error: X86-NEXT: expected string not found in input
# | ; X86-NEXT: jne .LBB9_3
# |             ^
# | <stdin>:167:17: note: scanning from here
# |  cmpl %esi, %edx
# |                 ^
# | <stdin>:168:2: note: possible intended match here
# |  jne .LBB9_1
# |  ^
# | /home/tcwg-buildbot/worker/clang-armv7-global-isel/llvm/llvm/test/CodeGen/X86/memcmp-pgso-x32.ll:219:13: error: X86-NEXT: expected string not found in input
# | ; X86-NEXT: jne .LBB11_2
# |             ^
# | <stdin>:214:17: note: scanning from here
# |  cmpl %edx, %ecx
# |                 ^
# | <stdin>:215:2: note: possible intended match here
# |  jne .LBB11_1
# |  ^
# | 
# | Input file: <stdin>
# | Check file: /home/tcwg-buildbot/worker/clang-armv7-global-isel/llvm/llvm/test/CodeGen/X86/memcmp-pgso-x32.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |             .
# |             .
# |             .
# |            70:  movl 8(%esp), %eax 
# |            71:  movzwl (%eax), %edx 
...

```

</details>

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