RFR: 8264928: Update to Xcode 12.4

[Ambarish Rapte]

On Thu, 8 Apr 2021 17:21:43 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> This updates the compiler used to build JavaFX on macOS to Xcode 12.4 (which includes the MacOSX11.1 sdk), which matches the compiler that will be used to build JDK 17, once openjdk/jdk#3388 is integrated.
> 
> As noted in the bug report, Xcode 12.4 needs macOS 10.15.4 (Catalina) or later to build. The produced artifacts will be able to run on earlier versions of macOS (for x86_64 systems anyway).

looks good to me. Verified build and sanity test.

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Marked as reviewed by arapte (Reviewer).

PR: https://git.openjdk.java.net/jfx/pull/460