RFR: 8305934: PPC64: Disable VMContinuations on Big Endian

[Richard Reingruber]

Disable VMContinuations on PPC64 big endian because there are known failures in jdk:jdk_loom tests.

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Commit messages:
 - Disable VMContinuations on big endian PPC

Changes: https://git.openjdk.org/jdk/pull/13449/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13449&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305934
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13449.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13449/head:pull/13449

PR: https://git.openjdk.org/jdk/pull/13449