RFR: 8349150: Support precompiled headers on AIX

[Matthias Baesken]

The clang compiler currently used on AIX should be able to support precompiled headers in the HS build (same as on Linux or macOS where clang is used).
However currently the precompiled headers feature is disabled on AIX (probably because the old xlc had issues with this feature).

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Commit messages:
 - JDK-8349150

Changes: https://git.openjdk.org/jdk/pull/23417/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23417&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349150
  Stats: 16 lines in 2 files changed: 7 ins; 6 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/23417.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23417/head:pull/23417

PR: https://git.openjdk.org/jdk/pull/23417