[jfx11u] RFR: 8266554: Change default macOS min version for aarch64 to 11.0

[Johan Vos]

Require at least MacOSX 11.0 to build on mac-AArch64.
Don't increase minimum SDK version when building on x86-64 (contrary to JDK-8265031)

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Commit messages:
 - Increase minimum SDK version when building on AArch64

Changes: https://git.openjdk.java.net/jfx11u/pull/21/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=21&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266554
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/21.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/21/head:pull/21

PR: https://git.openjdk.java.net/jfx11u/pull/21