RFR: build: update to JDK 14.0.1

[Erik Helin]

Hi all,

please review this patch that updates the JDK for Skara to version 14.0.1.

Testing:
- `sh gradlew images`
- `sh gradlew test`

Thanks,
Erik

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Commit messages:
 - build: update to JDK 14.0.1

Changes: https://git.openjdk.java.net/skara/pull/615/files
 Webrev: https://webrevs.openjdk.java.net/skara/615/webrev.00
  Stats: 14 lines in 3 files changed: 0 ins; 0 del; 14 mod
  Patch: https://git.openjdk.java.net/skara/pull/615.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/615/head:pull/615

PR: https://git.openjdk.java.net/skara/pull/615