[llvm] [llvm-dlltool] Remove the i386 underscore prefix from COFFImportFile::ImportName. NFC. (PR #98226)

[Martin Storsjö via llvm-commits]

================
@@ -691,10 +692,15 @@ Error writeImportLibrary(StringRef ImportName, StringRef Path,
       }
 
       if (!E.ImportName.empty() && Name != E.ImportName) {
+        StringRef Prefix = "";
+        if (Machine == IMAGE_FILE_MACHINE_I386 && AddUnderscores)
+          Prefix = "_";
----------------
mstorsjo wrote:

That's true, but I'm not entirely sure if this is a case we need to care about... For mingw mode, the existing `isDecorated` only triggers for fastcall/vectorcall/MSVC C++ symbols.

The whole mechanism for how the aliases find the symbol to point to is reworked in https://github.com/llvm/llvm-project/pull/98229 anyway.

I guess I can adjust the commit message to point out that this technically isn't fully NFC, but it's practically NFC for the cases we care about here.

https://github.com/llvm/llvm-project/pull/98226