RFR: 8376284: New test serviceability/sa/TestJhsdbJstackMixedCore.java from JDK-8374482 fails on Linux Alpine

[Yasumasa Suenaga]

TestJhsdbJstackMixedCore.java introduced in [JDK-8374482](https://bugs.openjdk.org/browse/JDK-8374482) failed on Alpine because musl-c does not provide the symbol of signal trampoline (`__restore_rt` on Linux Kernel for AMD64) as following:


java.lang.RuntimeException: '<signal handler called>' missing from stdout/stderr
at jdk.test.lib.process.OutputAnalyzer.shouldContain(OutputAnalyzer.java:253)
at TestJhsdbJstackMixedCore.runJstackMixed(TestJhsdbJstackMixedCore.java:62)
at TestJhsdbJstackMixedCore.main(TestJhsdbJstackMixedCore.java:74)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:335)
at java.base/java.lang.Thread.run(Thread.java:1516)


It would success if debuginfo is installed, but it should be skipped if the symbol is not available.
See JBS for details.

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Commit messages:
 - 8376284: New test serviceability/sa/TestJhsdbJstackMixedCore.java from JDK-8374482 fails on Linux Alpine

Changes: https://git.openjdk.org/jdk/pull/29480/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29480&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376284
  Stats: 122 lines in 2 files changed: 120 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/29480.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29480/head:pull/29480

PR: https://git.openjdk.org/jdk/pull/29480