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

[Phil Race]

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.

As a rule, we don't make changes to 3rd party code principally for the reason that it needs to be re-changed every time we upgrade. After some off-line discussion with the devs working on the AIX port of OpenJDK, we can make an exception here, and they will take care of re-applying it if it is still needed next time round.
And these changes only affect AIX of course ..

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Marked as reviewed by prr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13529#pullrequestreview-1392502653