[jdk20] RFR: 8299561: VaList.empty() doesn't return a list associated with the global scope

[Maurizio Cimadamore]

This patch fixes a long-standing conformance issue: `VaList.empty` is specified to return a `VaList` associated with the global scope, but in some platforms (Aarch64/Linux and x64/Linux) the empty list is associated with an implicit scope instead.

This doesn't make a lot of difference, given that the empty list is always stored in a static final in the underlying implementation - that said, it would be a good thing to rectify this conformance issue.

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Commit messages:
 - Initial push

Changes: https://git.openjdk.org/jdk20/pull/82/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20&pr=82&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299561
  Stats: 6 lines in 3 files changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk20/pull/82.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/82/head:pull/82

PR: https://git.openjdk.org/jdk20/pull/82