Add FreeBSD aarch64/x86_64 platforms' build.

[chirontt]

• part of the overall issue eclipse-platform/eclipse.platform.releng.aggregator#2959
• add 2 SWT binary modules for FreeBSD: org.eclipse.swt.gtk.freebsd.aarch64 and org.eclipse.swt.gtk.freebsd.x86_64
• changes made to the build.sh script and make_linux.mak (renamed to make_unix.mak) to support compiling FreeBSD native binaries for SWT.

To support cross-compiling from Linux to FreeBSD, for the same hardware architecture, a Docker container is made available in my fork with detailed instructions: https://github.com/chirontt/eclipse.platform.releng.aggregator/tree/master/cje-production/dockerfiles/alpine/freebsd-cross which will be submitted to the official repo at later stage.

[github-actions[bot]]

Test Results

0 files   -    526  0 suites   - 526   0s ⏱️ - 34m 10s 0 tests  -  4 336  0 ✅  -  4 326  0 💤  -   9  0 ❌  - 1  0 runs   - 16 576  0 ✅  - 16 464  0 💤  - 111  0 ❌  - 1 

Results for commit 448c3e1e. ± Comparison against base commit e63c07d1.

[akurtakov]

Closing as there doesn't seem to be a viable path ahead for this one.