RFR: 8267908: linux: thread_native_entry can scribble on stack frame

[David Holmes]

Please review this trivial fix to ensure we do not try to alloca zero bytes.

Thanks,
David

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Commit messages:
 - 8267908: linux: thread_native_entry can scribble on stack frame

Changes: https://git.openjdk.java.net/jdk/pull/4407/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4407&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267908
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4407.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4407/head:pull/4407

PR: https://git.openjdk.java.net/jdk/pull/4407