[llvm] [win][x64] Various fixes for unwind v2 (PR #154834)

[Daniel Paoliello via llvm-commits]

dpaoliello wrote:

> LLVM Buildbot has detected a new failure on builder `cross-project-tests-sie-ubuntu-dwarf5` running on `doug-worker-1b` while building `llvm` at step 6 "test-build-unified-tree-check-cross-project".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/163/builds/25626

Unrelated to my change:
```
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**                                    **
** This is a bug in DExTer.           **
**                                    **
**                  Please report it. **
**                                    **
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```

https://github.com/llvm/llvm-project/pull/154834