RFR: 8363910: Avoid tuning for Power10 CPUs on Linux ppc64le when gcc < 10 is used

[Lutz Schmidt]

On Wed, 23 Jul 2025 12:23:04 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> Older gcc version (8, 9) do not support the -mtune=power10 flag. We should set this only when recent gcc versions are used.

Just for my understanding:
If `-mtune=power10` is already in the arguments, nothing is changed/added. In any other case (e.g. `-mtune=power11`), the string `-mtune=power8` is added. Is that intended?

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

Changes requested by lucy (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26442#pullrequestreview-3052380845