[compiler-rt] [llvm] [msan] Add 32-bit platforms support (PR #109284)

[Vitaly Buka via llvm-commits]

================
@@ -6043,8 +6178,9 @@ struct VarArgGenericHelper : public VarArgHelperBase {
   void finalizeInstrumentation() override {
     assert(!VAArgSize && !VAArgTLSCopy &&
            "finalizeInstrumentation called twice");
+
     IRBuilder<> IRB(MSV.FnPrologueEnd);
-    VAArgSize = IRB.CreateLoad(IRB.getInt64Ty(), MS.VAArgOverflowSizeTLS);
----------------
vitalybuka wrote:

there is 
```
VAArgOverflowSizeTLS =
      getOrInsertGlobal(M, "__msan_va_arg_overflow_size_tls", IRB.getInt64Ty());
```

https://github.com/llvm/llvm-project/pull/109284