RFR: 8291822: ARM: fix build warnings with GCC11

[Marc R. Hoffmann]

Same workaround was applied for other platforms in JDK-8270083 and JDK-8271869

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Commit messages:
 - 8291822: ARM: fix build warnings with GCC11

Changes: https://git.openjdk.org/jdk/pull/9727/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9727&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291822
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9727.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9727/head:pull/9727

PR: https://git.openjdk.org/jdk/pull/9727