[jfx25u] RFR: 8329874: JavaFX debug builds fail on Linux

[Jay Bhaskar]

A clean backport to jfx25u. The patch fixes linux debug build error. The build is ok with fix and fails without fix.

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Commit messages:
 - Backport 35c1e39cddc6c3d15118b61f99d67f2aba7641c4

Changes: https://git.openjdk.org/jfx25u/pull/16/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx25u&pr=16&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329874
  Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx25u/pull/16.diff
  Fetch: git fetch https://git.openjdk.org/jfx25u.git pull/16/head:pull/16

PR: https://git.openjdk.org/jfx25u/pull/16