[llvm] [llvm] Make charset constexpr (NFC) (PR #137535)

[A. Jiang via llvm-commits]

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@@ -49,7 +49,7 @@ std::string llvm::logicalview::flattenedFilePath(StringRef Path) {
   std::string Name(Path);
   std::transform(Name.begin(), Name.end(), Name.begin(), tolower);
 
-  const char *CharSet = "/\\<>.:%*?|\" ";
+  constexpr char *CharSet = "/\\<>.:%*?|\" ";
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frederick-vs-ja wrote:

You seemed to change the type of `CharSet` accidentally.
```suggestion
  constexpr const char *CharSet = "/\\<>.:%*?|\" ";
```

https://github.com/llvm/llvm-project/pull/137535