RFR: 8338428: Print final VM flags for task [v2]

[David Holmes]

On Sun, 12 Jan 2025 15:47:15 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> Some VM flags might depend on the environment and it makes sense to log final flags so it is possible to get their value when investigating failures.
>> 
>> I added them to VMProps, so it is always dump final flags before running tests using "-XX:+PrintFlagsFinal".
>> 
>> Update:
>> There were intermittent compilation failures when I tried to use classes from testlibrary, so I rewrtite the code without them.
>
> Leonid Mesnik has updated the pull request incrementally with one additional commit since the last revision:
> 
>   The test lib is not ued

So it is once per run of jtreg effectively? Even so while the cost to the test task is negligible the accumulated cost in machine time (which someone is paying for) is not. Everything else in `VMProps` queries the VM running `VMProps` and this should do the same. We should add a whitebox API to either retrieve, or directly dump, the final flags values.

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PR Comment: https://git.openjdk.org/jdk/pull/23054#issuecomment-2594292192