[jdk17u-dev] RFR: 8293998: [PPC64] JfrGetCallTrace: assert(_pc != nullptr) failed: must have PC

[Martin Doerr]

Backport of JDK-8293998. Linux part applies cleanly modulo file renaming. AIX code was not yet available. I've taken the code from jdk head. It's identical to the linux version except `uc_mcontext` accesses.

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Commit messages:
 - Backport 14c6ac457d319a2e7f9cc9e7355c81c421a065dd

Changes: https://git.openjdk.org/jdk17u-dev/pull/740/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=740&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293998
  Stats: 76 lines in 2 files changed: 65 ins; 1 del; 10 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/740.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/740/head:pull/740

PR: https://git.openjdk.org/jdk17u-dev/pull/740