Add support for FreeBSD

[chirontt]

Update: since there's no objection, I'm now submitting PRs to various Eclipse repositories for this issue. Here's the central TODO list to keep track of various tasks done and/or under way:

• add support for FreeBSD to eclipse.jdt.debug submodule
  • Add FreeBSD platforms' build. eclipse-jdt/eclipse.jdt.debug#676
• add support for FreeBSD to eclipse.jdt.ui submodule
  • Add FreeBSD platforms' build. eclipse-jdt/eclipse.jdt.ui#2170
• add support for FreeBSD to eclipse.pde submodule
  • Add FreeBSD platforms' build. eclipse-pde/eclipse.pde#1726
• add support for FreeBSD to eclipse.platform submodule
  • Add FreeBSD platforms' build. eclipse.platform#1831
  • compile the file system natives for FreeBSD. If cross-compiling from Linux is needed, use the freebsd-cross Docker container as a suitable cross-compile tool - details are in its README file for x86_64 and/or for aarch64.
• add support for FreeBSD to eclipse.platform.swt submodule
  • Add FreeBSD aarch64/x86_64 platforms' build. eclipse.platform.swt#2044
  • compile the SWT natives for FreeBSD. If cross-compiling from Linux is needed, use the freebsd-cross Docker container as a suitable cross-compile tool - details are in its README file for x86_64 and/or for aarch64.
• add support for FreeBSD to eclipse.platform.ui submodule
  • Add FreeBSD platforms' build. eclipse.platform.ui#2933
• add support for FreeBSD to equinox submodule
  • Add FreeBSD platforms' build. eclipse-equinox/equinox#929
  • compile the launcher natives for FreeBSD. If cross-compiling from Linux is needed, use the freebsd-cross Docker container as a suitable cross-compile tool - details are in its README file for x86_64 and/or for aarch64.
• add support for FreeBSD to equinox.p2 submodule
  • Add FreeBSD platforms' build. eclipse-equinox/p2#788
• add support for FreeBSD to eclipse.platform.releng.aggregator supermodule
  • Add FreeBSD platforms' build. #2994

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As discussed in #2275

I have been enhancing and building the Eclipse SDKs for FreeBSD in my own fork, and have manually tested them regularly, and successfully, on my own FreeBSD boxes for x86_64 and/or aarch64 architectures. It's time to submit them to the official repos, I guess. Please provide your opinions whether it's worthwhile to officially support FreeBSD builds or not.

I understand that there are no FreeBSD platforms on the official build farm, so it's a bit tricky to officially compile the native binaries for FreeBSD, and thus there won't be any automated tests for the FreeBSD builds (assuming current situation for the near future.) For now, for the native compiling, I have enhanced some existing Docker container to cross-compile the C code from Linux (Alpine Linux, to be exact) to FreeBSD binaries; its README file shows details in cross-compiling the SWT and Equinox launcher binaries to FreeBSD.

If the team supports this FreeBSD build initiative. I will start submitting PRs to various submodule repos, and this issue will become the co-ordination point for the PRs. Of course, any help from the team is quite valuable and is greatly appreciated.