RFR: 8241629: [macos10.15] Long startup delay playing media over https on Catalina

[Alexander Matveev]

https://bugs.openjdk.java.net/browse/JDK-8241629

We used to link with system provided libffi (due to a bug in Makefile) and for some reason GLib signals did not work
correctly and thus we did not able to build dynamic pipelines. We did not switch to AVFoundation until timeout is
reached while waiting for GStreamer to start playing or report us an error. Fixed by linking GLib with libffi which we
build, like we do for other platforms.

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Commit messages:
 - 8241629: [macos10.15] Long startup delay playing media over https on Catalina

Changes: https://git.openjdk.java.net/jfx/pull/179/files
 Webrev: https://webrevs.openjdk.java.net/jfx/179/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8241629
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jfx/pull/179.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/179/head:pull/179

PR: https://git.openjdk.java.net/jfx/pull/179