RFR: 8351154: Use -ftrivial-auto-var-init=pattern for clang too

[Magnus Ihse Bursie]

This is a trivial (no pun intended) follow-up to [JDK-8345627](https://bugs.openjdk.org/browse/JDK-8345627), which just enables the -ftrivial-auto-var-init=pattern on debug builds for clang too. In contrast to gcc, the clang option did not trigger any additional warnings, so it is just about enabling the flag for debug builds.

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Commit messages:
 - 8351154: Use -ftrivial-auto-var-init=pattern for clang too

Changes: https://git.openjdk.org/jdk/pull/23892/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23892&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351154
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23892.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23892/head:pull/23892

PR: https://git.openjdk.org/jdk/pull/23892