RFR: 8263204: Add Gradle Wrapper Validation Action

[Kevin Rushforth]

On Mon, 8 Mar 2021 22:55:18 GMT, John Neffenger <github.com+1413266+jgneff at openjdk.org> wrote:

>> Okay, this is looking better! The validation took only 23 seconds, and GitHub shows the following results:
>> 
>> ![some-checks-were-not-successful-2](https://user-images.githubusercontent.com/1413266/110390566-0b7ac680-801b-11eb-8090-f1548046094e.png)
>> 
>> The screenshot below shows the notification I received by e-mail:
>> 
>> ![run-failed-message](https://user-images.githubusercontent.com/1413266/110390602-17ff1f00-801b-11eb-9870-c5f955b4739c.png)
>> 
>> Now we'll see whether the three build jobs still run in parallel when the wrapper validation succeeds. My next commit will restore the Gradle Wrapper JAR file.
>
> Looks good: two preliminary checks followed conditionally by the three concurrent build jobs:
> 
> ![some-checks-haven’t-completed-yet](https://user-images.githubusercontent.com/1413266/110392468-d15ef400-801d-11eb-8a1c-1bf49ed32a2a.png)
> 
> Once the build jobs finish, this pull request is finally ready for review. Thanks for your timely help, Kevin.

Yep, they are running in parallel. And this provides a nice view:

https://github.com/jgneff/jfx/actions/runs/633879096

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PR: https://git.openjdk.java.net/jfx/pull/419