RFR: Add Windows support in GitHub actions

[Maurizio Cimadamore]

On Thu, 11 Apr 2024 17:05:33 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> We currently don't run tests in GitHub actions on Windows. This can mean that a build failure on Windows may be missed (as seen recently). This PR adds support for running tests on Windows to the GitHub actions workflow.
> 
> Some notes about the changes:
> - We can not build jtreg on Windows, so I've added a separate job which builds it on Ubuntu and then caches it. Then the main test job restores it from this cache. (FWIW, this cache is private/can not be downloaded outside of the actions)
> - The `oracle-actions/setup-java` action we use gives us back a Windows path on Windows, which I don't think we can easily handle in bash, so I've created a Windows specific step for extracting the downloaded toolchain JDK
> - Added caches also for LLVM/libclang and the toolchain JDK, so we don't have to download them all the time, and testing is faster.
> - For that reason, I've added a step that creates a trimmed-down 'image' of the LLVM package with only the bits that we need, so that we can only cache those bits, instead of the entire LLVM package.

Marked as reviewed by mcimadamore (Reviewer).

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PR Review: https://git.openjdk.org/jextract/pull/235#pullrequestreview-1995366725