[jdk17] RFR: 8268602: a couple runtime/os tests don't check exit code

[Igor Ignatyev]

Hi all,

could you please review this trivial and test-only patch that adds checks of exit code to two `runtime/os` tests?
from JBS:
> `runtime/os/TestUseCpuAllocPath.java` and `AvailableProcessors.java` spawn new JVMs but don't check their exit code which might lead to both type-I and type-II errors

testing: ``runtime/os` on `{linux,windows,macosx}-x64`

Thanks,
-- Igor

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Commit messages:
 - copyright
 - 8268602

Changes: https://git.openjdk.java.net/jdk17/pull/25/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=25&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268602
  Stats: 4 lines in 2 files changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/25.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/25/head:pull/25

PR: https://git.openjdk.java.net/jdk17/pull/25