[llvm] Update Windows release script (PR #215749)

[Alexandre Ganea via llvm-commits]

aganea wrote:

> Considering the RFC, is it still worth pursuing the, more or less, one-to-one Python rewrite? I was mostly done implementing it, but it's probably not worth finishing if we are to rebuild the Windows build machinery from the ground up.

Let's land this change, then I'll send a PR for the Powershell script. I feel Powershell is more natural choice for Windows developers - as far as I am concerned. But feel free to disagree. I don't think overall any of the two choices (Python or Powershell) wins, they both have pros and cons and will come up most likely to the same amount of LoC.

https://github.com/llvm/llvm-project/pull/215749