PR #475 from Achilleas Mantzios rebased

... with build/freebsd.md updated accordingly.

src/site/markdown/build/freebsd.md

@@ -1,23 +1,7 @@
 # Building on FreeBSD
 
-At one time, [FreeBSD][]'s threading library would malfunction if it was
-dynamically loaded after the start of a program that did not use threads
-itself. That was a problem for PL/Java on FreeBSD, because PostgreSQL
-itself does not use threads, but Java does. The only known workaround was
-to build PostgreSQL itself from source, with the thread library included
-in linking.
-
-The same problem was [reported to affect other PostgreSQL extensions][rep]
-such as `plv8` and `imcs` also.
-
-The [manual page for FreeBSD's libthr][manthr] was edited
-[in February 2015][thrdif] to remove the statement of that limitation,
-and the updated manual page appears first in [FreeBSD 10.2][rel102],
-so in FreeBSD 10.2 or later, PL/Java (and other affected extensions)
-may work without the need to build PostgreSQL from source.
+Building on [FreeBSD][] should proceed just as it does on Linux,
+as of late 2023, according to Achilleos Mantzios, who provided the patch
+adding the necessary build rules.
 
 [FreeBSD]: https://www.freebsd.org/
-[rep]: https://lists.freebsd.org/pipermail/freebsd-hackers/2014-April/044961.html
-[manthr]: https://www.freebsd.org/cgi/man.cgi?query=libthr&apropos=0&sektion=3&manpath=FreeBSD+10.2-RELEASE&arch=default&format=html
-[thrdif]: https://svnweb.freebsd.org/base/head/lib/libthr/libthr.3?r1=272153&r2=278627
-[rel102]: https://www.freebsd.org/releases/10.2R/announce.html