RFR: 8367969: C2: compiler/vectorapi/TestVectorMathLib.java fails without UnlockDiagnosticVMOptions

[Emanuel Peter]

Adding missing `-XX:+UnlockDiagnosticVMOptions`.

Seems the test from https://github.com/openjdk/jdk/pull/27263 was not tested with the product build before integration.

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Commit messages:
 - JDK-8367333

Changes: https://git.openjdk.org/jdk/pull/27359/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27359&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367969
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27359.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27359/head:pull/27359

PR: https://git.openjdk.org/jdk/pull/27359