[jfx17u] RFR: 8378703: use xcode15 for macos build on jfx17u

[Johan Vos]

Bump Xcode version to the same version currently used in head (15.4+1.0)
Before moving to Xcode 15, we need to solve some build issues. This is tackled in https://github.com/openjdk/jfx17u/pull/254

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Commit messages:
 - Bump Xcode version to the same version currently used in head (15.4+1.0)

Changes: https://git.openjdk.org/jfx17u/pull/255/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx17u&pr=255&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378703
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx17u/pull/255.diff
  Fetch: git fetch https://git.openjdk.org/jfx17u.git pull/255/head:pull/255

PR: https://git.openjdk.org/jfx17u/pull/255