[clang] [llvm] [RISCV][Clang][TargetParser] Support getting feature unaligned-scalar-mem from mcpu. (PR #71513)

[Francesco Petrogalli via cfe-commits]

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@@ -60,9 +60,14 @@ static void EmitRISCVTargetDef(RecordKeeper &RK, raw_ostream &OS) {
     if (MArch.empty())
       MArch = getMArch(*Rec);
 
+    bool FastUnalignedAccess =
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fpetrogalli wrote:

```suggestion
    const bool FastUnalignedAccess =
```

https://github.com/llvm/llvm-project/pull/71513