[jfx11u] RFR: 8276174: JavaFX build fails on macOS aarch64

Sat Apr 30 13:57:09 UTC 2022

Backport to `jfx11u` so we can build on macOS / aarch64 without needing to specify `-PCOMPILE_TARGET=arm64`. It isn't a clean backport, since I also had to include the definition of `IS_AARCH64` which is present in mainline, but not in `jfx11u` (it was added as part of another unrelated fix that isn't backported to `jfx11u`).

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Commit messages:
 - 8276174: JavaFX build fails on macOS aarch64

Changes: https://git.openjdk.java.net/jfx11u/pull/100/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=100&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276174
  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/100.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/100/head:pull/100

PR: https://git.openjdk.java.net/jfx11u/pull/100