FreeBSD support has been broken for a long time, probably since
https://github.com/tinygo-org/tinygo/pull/1860 (merged in May). Nobody
has complained yet, so I am going to assume nobody uses it.
This doesn't remove support for FreeBSD entirely: the code necessary to
build TinyGo on FreeBSD is still there. It just removes the code
necessary to build binaries targetting FreeBSD. But again, it could very
well be broken as we don't test it.
If anybody wants to re-enable support for FreeBSD, they would be welcome
to do that. But I think it would at the very least need a smoke test of
some sort.