RFR: 8290313: Produce warning when user specified java.io.tmpdir directory doesn't exist

[Weibing Xiao]

print warning message for java.io.tmpdir when it is set through the command line and the value is not good for creating file folder.

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Commit messages:
 - remove extra line
 - warning message for java.io.tmpdir

Changes: https://git.openjdk.org/jdk/pull/11174/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11174&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290313
  Stats: 146 lines in 4 files changed: 142 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/11174.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11174/head:pull/11174

PR: https://git.openjdk.org/jdk/pull/11174