RFR: 8254670: SVE test uses linux-specific api

[Ningsheng Jian]

The SVE JNI test uses linux-specific api in native code, which is invalid with Windows/AArch64 and macOS/AArch64 ports
in. Fixed by simply reducing the test to Linux only.

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Commit messages:
 - 8254670: SVE test uses linux-specific api

Changes: https://git.openjdk.java.net/jdk/pull/778/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=778&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254670
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/778.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/778/head:pull/778

PR: https://git.openjdk.java.net/jdk/pull/778