RFR: 8342295: compiler/jvmci/TestJVMCISavedProperties.java fails due to garbage in output

[Tomáš Zezula]

The `compiler/jvmci/TestJVMCISavedProperties` test fails due to overlapping output from the saved system properties. The initialization of `savedProperties` in `jdk.vm.ci.services.Services` is correctly synchronized, the issue suggests that two separate libjvmci compiler isolates are each printing their own set of saved properties.

In a successful test run, the `CompileBroker` thread aborts the VM before it completes initialization, displaying the error message `Cannot use JVMCI compiler: Value of jvmci.Compiler is “null”` (due to the `-Djvmci.Compiler=null` setting), and the message `DONE IN MAIN` is never printed. However, in the failed test output, the `DONE IN MAIN` message appears, indicating that the VM initialization completed and created the `JVMCIRuntime` instance. The `CompileBroker` thread might have concurrently initialized `JVMCIRuntime` in another isolate. Since each `JVMCIRuntime` initialization outputs system properties, this is likely the cause of the overlapping output.

The proposed solution is to use the `-XX:+EnableJVMCI` flag instead of `-XX:+UseJVMCICompiler`, to avoid this issue.

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Commit messages:
 - 8342295: compiler/jvmci/TestJVMCISavedProperties.java fails due to garbage in output

Changes: https://git.openjdk.org/jdk/pull/21583/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21583&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342295
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21583.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21583/head:pull/21583

PR: https://git.openjdk.org/jdk/pull/21583