RFR: 8286089: Intermittent WebKit build failure on macOS in JavaScriptCore

[Jay Bhaskar]

Issue: Error copying file (if different) from Source/JavaScriptCore/Scripts/wkbuiltins/builtins_generate_separate_header.py" to "modules/javafx.web/build/mac/Release/JavaScriptCcripts/builtins_generate_separate_header.py".

Root cause: The number of build threads more than 8, causing a synchronization issue for builtins_generate_separate_header.py, the file needs to be copied before use at build dir

Solution: Use the sleep of 1 second and retry 10 times to copy in CMakeList.txt and execute using the execute_process cmake command

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Commit messages:
 - 8286089: Fix Build error mac osx 11

Changes: https://git.openjdk.org/jfx/pull/1073/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1073&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286089
  Stats: 26 lines in 1 file changed: 26 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1073.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1073/head:pull/1073

PR: https://git.openjdk.org/jfx/pull/1073