RFR: 8372196: Compile error in cgroup code on Linux when using clang after JDK-8365606

[Kim Barrett]

Please review this trivial fix for a build failure when using clang on Linux.

Testing: mach5 tier1 on linux. Local build with clang19 on linux-aarch64.

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Commit messages:
 - add missing override specifieres

Changes: https://git.openjdk.org/jdk/pull/28402/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28402&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372196
  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/28402.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28402/head:pull/28402

PR: https://git.openjdk.org/jdk/pull/28402