RFR: 8317370: JavaFX runtime version is wrong at runtime

[John Neffenger]

Please review these changes to the build timestamp and to the JavaFX runtime version available in the system properties.

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Commit messages:
 - 8317370: JavaFX runtime version is wrong at runtime

Changes: https://git.openjdk.org/jfx/pull/1253/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1253&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317370
  Stats: 116 lines in 3 files changed: 66 ins; 39 del; 11 mod
  Patch: https://git.openjdk.org/jfx/pull/1253.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1253/head:pull/1253

PR: https://git.openjdk.org/jfx/pull/1253