RFR: 8338428: Print final VM flags for task [v4]

[Leonid Mesnik]

> 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:

  Added diagnostic flag

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23054/files
  - new: https://git.openjdk.org/jdk/pull/23054/files/d2f3b1c2..28b05e9b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23054&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23054&range=02-03

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23054.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23054/head:pull/23054

PR: https://git.openjdk.org/jdk/pull/23054