RFR: 8345669: RISC-V: fix client build failure due to AlignVector after JDK-8343827

[Hamlin Li]

Hi,
Can you help to review this simple fix?
Thanks!

Previously in JDK-8343827, AlignVector was enabled conditionally, but the code was put in common path (shared with non-C2 code), but in fact this flag is only for C2.

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/22605/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22605&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345669
  Stats: 8 lines in 1 file changed: 4 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22605.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22605/head:pull/22605

PR: https://git.openjdk.org/jdk/pull/22605