[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)

[Mingming Liu via llvm-commits]

mingmingl-llvm wrote:

In both windows and linux, the failed tests are irrelevant. Going to merge this change.

```
  ********************
  Failed Tests (2):
    LLVM :: CodeGen/X86/memcmp-pgso-x32.ll
    LLVM :: CodeGen/X86/memcmp-pgso.ll
```

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