RFR: 8375094: RISC-V: Fix client builds after JDK-8368732

Tue Jan 13 05:01:32 UTC 2026

Hi,
Can you help to review this patch? Thanks!

[JDK-8368732](https://bugs.openjdk.org/browse/JDK-8368732) broke RISC-V client builds because `AlignVector` is a C2-only option.
This pr is to put `AlignVector` under COMPILER2 macro protection.

Builds tested w/ and w/o `--with-jvm-variants=client`.

-------------

Commit messages:
 - 8375094: RISC-V: Fix client builds after JDK-8368732

Changes: https://git.openjdk.org/jdk/pull/29182/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29182&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375094
  Stats: 10 lines in 1 file changed: 5 ins; 5 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29182.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29182/head:pull/29182

PR: https://git.openjdk.org/jdk/pull/29182