[jfx11u] RFR: 8264928: Update to Xcode 12.4

[Kevin Rushforth]

Almost clean backport to jfx11u (clean except for surrounding context in `build.properties`). Tested on all three platforms, along with my other in-progress backports, all of which are aggregated in my [`kevinrushforth:test-kcr-11.0.12`](https://github.com/kevinrushforth/jfx11u/commits/test-kcr-11.0.12) branch.

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Commit messages:
 - 8264928: Update to Xcode 12.4

Changes: https://git.openjdk.java.net/jfx11u/pull/14/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=14&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264928
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/14.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/14/head:pull/14

PR: https://git.openjdk.java.net/jfx11u/pull/14