RFR: 8339772: serviceability/sa/TestJhsdbJstackUpcall.java fails on Linux ppc64le

[Martin Doerr]

The SA model of the UpcallStub doesn't work reliably on PPC64. We can use the Backchain which works for all Power Architecture 64-Bit ELF ABI compliant frames. (The backtrace should stop when hitting a non-compliant frame which can occur with some compiler options. Also see comment in JBS issue.)
"test/hotspot/jtreg/serviceability" tests have passed with this PR.

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Commit messages:
 - 8339772: serviceability/sa/TestJhsdbJstackUpcall.java fails on Linux ppc64le

Changes: https://git.openjdk.org/jdk/pull/21092/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21092&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339772
  Stats: 34 lines in 1 file changed: 1 ins; 31 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21092.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21092/head:pull/21092

PR: https://git.openjdk.org/jdk/pull/21092