RFR: JDK-8304291: [AIX] Broken build after JDK-8301998

[Adam Farley]

On Wed, 19 Apr 2023 10:38:19 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> After the latest harfbuzz update, the AIX build is broken.  The old clang compiler from xlc16 does not compile harfbuzz correctly.
> First issue in hb-algs.hh is that xlc16 clang still sets some GNUC-related macros, so we do not run into the  `__clang_major__ >= 8`  check that should prevent to try to compile  `__builtin_mul_overflow`   with ancient clang.
> The other issue in  `hb-subset.cc`  is a bit tricky and has been observed as well on macOS when very old clang versions were used.
> 
> Probably we can get rid of those 2 workarounds in some months after switching to xlc17 which includes a rather new clang version.

Note: I asked the bot for help because the documentation [here](https://wiki.openjdk.org/display/SKARA/Pull+Request+Commands#PullRequestCommands-/backport), along with examples [here](https://github.com/openjdk/jdk/pull/8205#issuecomment-1153856655) and [here](https://github.com/openjdk/jdk/pull/4128#issuecomment-873779183), seem to imply that backport is not a valid command for closed PRs, so I wanted to know what my options were.

I mean, options aside from the somewhat lengthier process detailed [here](https://wiki.openjdk.org/display/SKARA/Backports), which I'll do if I must.

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PR Comment: https://git.openjdk.org/jdk/pull/13529#issuecomment-1584465618