RFR: 8254691: Enable GitHub actions for jfx repo

[Kevin Rushforth]

On Tue, 27 Oct 2020 19:02:40 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> ### Note to reviewers:
>> 
>> If you want to test this yourself you can pull the PR branch into a branch in your local repo and push it to your personal fork. Something like the following should work for you, assuming that you are in your local repo with `origin` pointing to your personal fork:
>> 
>> git fetch https://github.com/openjdk/jfx.git pull/338/head:pr-338
>> git push -u origin pr-338
>> 
>> Then you will be able to see the GitHub action workflow and track its progress by clicking on the "Actions" tab on your personal fork repo page.
>
> See PR #339 for an example (using an intentionally injected failure) of what a failed build or test will look like.

I merged `master` into my local branch so it would run the tests again on an up-to-date repo.

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PR: https://git.openjdk.java.net/jfx/pull/338