doc: documenting a bit more FreeBSD case

FreeBSD provides more up to date compilers than
the one provided by the system.

PR-URL: https://github.com/nodejs/node/pull/30325


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: James M Snell <jasnell@gmail.com>