RFR: 8299330: Minor improvements in MSYS2 Workflow handling [v11]

[Julian Waters]

On Thu, 12 Jan 2023 14:28:54 GMT, Julian Waters <jwaters at openjdk.org> wrote:

>> MSYS2 should be more appropriately installed into the runner's temporary directory rather than inside the newly checked out repository containing all the JDK's source code, as doing so may interfere with the build process and cause weird corner cases in the submitted actions workflow. On windows, the bash it uses is also not run properly, which we should address
>
> Julian Waters has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Move shell env call to build-windows.yml

Alright, configure stage passes. @ GitHub for the love of god, please implement setting `merge_commit_sha` from the API so we can mark our Pull Requests as having been properly merged

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PR: https://git.openjdk.org/jdk/pull/11782