RFR: 8293456: runtime/os/TestTracePageSizes.java sub-tests fail with "AssertionError: No memory range found for address: NNNN"

[Brian Burkhalter]

Do not use direct copy if the source size is zero as this may fail on some configurations but appear to succeed.

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Commit messages:
 - 8293456: runtime/os/TestTracePageSizes.java sub-tests fail with "AssertionError: No memory range found for address: NNNN"

Changes: https://git.openjdk.org/jdk/pull/10204/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10204&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293456
  Stats: 10 lines in 2 files changed: 3 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/10204.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10204/head:pull/10204

PR: https://git.openjdk.org/jdk/pull/10204