RFR: 8342768: GTest AssemblerX86.validate_vm failed: assert(VM_Version::supports_bmi1()) failed: tzcnt instruction not supported

[hanklo6]

The `tzcnt` instruction requires the VM to support `bmi1` feature, which we set directly when running the test.

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Commit messages:
 - Set bmi1 flag in test

Changes: https://git.openjdk.org/jdk/pull/21644/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21644&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342768
  Stats: 2 lines in 2 files changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21644.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21644/head:pull/21644

PR: https://git.openjdk.org/jdk/pull/21644