RFR: 8314488: Compile the JDK as C++17 [v6]

[Matthias Baesken]

On Fri, 12 Jan 2024 06:32:34 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> > Thanks! We may switch to clang 14 on MacOS at some point of time, but it's better to have that disentangled. Some people build JDK 11 and 23 on the same machine and that is easier if they don't have to switch Xcode.
> 
> I think the minimum clang version should not be greater than what’s provided by the minimum Open XL C/C++ version.
> 
> If the aix-ppc port only requires Open XL C/C++ 17.1.1 then that’s clang 13. If the aix-ppc port were to instead jump further forward, to 17.1.2, then that’s clang 15.
> 
> I've asked the aix-ppc folks if requiring 17.1.2 would be okay, but haven't heard back yet.

We at SAP use  and document xlC  17.1.1.4   for jdk22 (use the same for jdk23)
https://wiki.openjdk.org/display/Build/Supported+Build+Platforms

version 17.1.1.4  is already clang15 (at least that's what the compiler output is telling me) 

/opt/IBM/openxlC/17.1.1/bin/ibm-clang++_r -v
IBM Open XL C/C++ for AIX 17.1.1 (5725-C72, 5765-J18), version 17.1.1.4, clang version 15.0.0 (build ca7115e)
Target: powerpc-ibm-aix7.2.0.0

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PR Comment: https://git.openjdk.org/jdk/pull/14988#issuecomment-1888583559