RFR: 8338290: Xcode project generator for hotspot

[Magnus Ihse Bursie]

Add a make target to generate an Xcode project file for Hotspot. 

This PR is the result of a cooperation between me and @gerard-ziemski. Gerard developed the original Xcode generator (as a stand-alone project in https://github.com/gerard-ziemski/xcode), and I have written the build system "glue" to integrate it, and refactored the code to modern JDK standards.

Usage: Run `make hotspot-xcode-project`, and an Xcode project file will be generated in `build/$BUILD/xcode`. You can also have this automatically opened in Xcode by `make open-hotspot-xcode-project` (but note that for repeated runs of this, `make open-hotspot-xcode-project-only` is greatly preferred).

-------------

Commit messages:
 - Remove inadvertent tab (fixes jcheck complaint)
 - Move copying of helper scripts to makefile, and chmod them +x
 - 8007737: Xcode generator project for hotspot

Changes: https://git.openjdk.org/jdk/pull/20564/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20564&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338290
  Stats: 1776 lines in 14 files changed: 1762 ins; 5 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/20564.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20564/head:pull/20564

PR: https://git.openjdk.org/jdk/pull/20564