RFR: 8253689: [s390] Use flag kind diagnostic for platform specific flags

[Lutz Schmidt]

On Tue, 29 Sep 2020 20:52:17 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> Current platform implementation (globals_s390.hpp) uses regular product flags for everything.
> These platform specific flags were never intended for official support. They are only there to diagnose issues and find
> workarounds. So flag kind "diagnostic" fits better.
> 
> CSR: https://bugs.openjdk.java.net/browse/JDK-8253691

This is an overdue cleanup. Thanks for taking care. The changes look good to me. Reviewed.

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

Marked as reviewed by lucy (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/414