RFR: JDK-8306304: Fix xlc17 clang warnings in ppc and aix code [v2]

[JoKern65]

On Wed, 24 May 2023 03:13:34 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Strange the last resulting change I see is
>> `struct shmid_ds shm_buf{};`
>
> That's not what I see in this PR, and not what I see in the repository after the integration.  Where are you seeing
> that?  (If in your local repository, maybe you forgot a push to the PR?)

I checked it directly in repository
[https://github.com/openjdk/jdk/blob/master/src/hotspot/os/aix/os_aix.cpp](https://github.com/openjdk/jdk/blob/master/src/hotspot/os/aix/os_aix.cpp)
And there I see the desired
`struct shmid_ds shm_buf{};`

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

PR Review Comment: https://git.openjdk.org/jdk/pull/13953#discussion_r1205094231