RFR: 8328647: TestGarbageCollectorMXBean.java fails with C1-only and -Xcomp

[Stefan Karlsson]

Trivial patch to turn off this test when running with -Xcomp. The test doesn't expect to see GCCauses related to the code cache, so stop running with flags puts pressure on the code cache.

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Commit messages:
 - 8328647: TestGarbageCollectorMXBean.java fails with C1-only and -Xcomp

Changes: https://git.openjdk.org/jdk/pull/18421/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18421&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328647
  Stats: 2 lines in 2 files changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18421.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18421/head:pull/18421

PR: https://git.openjdk.org/jdk/pull/18421