[llvm] Introduce MCAsmInfo::UsesSetToEquateSymbol and prefer = to .set (PR #142289)

[Lei Huang via llvm-commits]

lei137 wrote:

@MaskRay A lit test failed on https://lab.llvm.org/buildbot/#/builders/64/builds/4195, are you able to put in a quick fix?
```
Input file: <stdin>
Check file: /home/llvm/llvm-external-buildbots/workers/aix-ppc64/clang-ppc64-aix/llvm-project/llvm/test/MC/AsmParser/include.ll
-dump-input=help explains the following input dump.
Input was:
<<<<<<
            1:  .file "/home/llvm/llvm-external-buildbots/workers/aix-ppc64/clang-ppc64-aix/llvm-project/llvm/test/MC/AsmParser/include.ll",,"LLVM version 21.0.0git" 
check:13'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
            2:  .csect ..text..[PR],5 
check:13'0     ~~~~~~~~~~~~~~~~~~~~~~~
            3:  .rename ..text..[PR],"" 
check:13'0     ~~~~~~~~~~~~~~~~~~~~~~~~~
            4:  # Start of file scope inline assembly 
check:13'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            5:  
check:13'0     ~
            6:  
check:13'0     ~
            7: .set MODULE, 1 
check:13'0     ~~~~~~~~~~~~~~~
check:13'1          ?          possible intended match
            8:  
check:13'0     ~
            9:  
check:13'0     ~
           10:  
check:13'0     ~
           11:  # End of file scope inline assembly 
check:13'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           12:  .machine "PWR7" 
check:13'0     ~~~~~~~~~~~~~~~~~
            .
            .
            .
>>>>>>
--
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```

https://github.com/llvm/llvm-project/pull/142289