37.10.5 - outdated compiler for FreeBSD

Hello list,

The "37.10.5. Compiling and Linking Dynamically-Loaded Functions" (
https://www.postgresql.org/docs/devel/xfunc-c.html#DFUNC) mentions outdated
compiler for FreeBSD (gcc). As of FreeBSD 13.0 and going forward, all
supported architectures abandoned gcc and use LLVM/clang. The FreeBSD 13.0
is already EOL, therefore all supported FreeBSD releases for all
architectures have clang as the default compiler. It is still allowed to
use gcc but it's not installed by default.

You can confirm that in the release notes for FreeBSD 13.0 (
https://www.freebsd.org/releases/13.0R/relnotes/#userland-programs) and in
other places in the FreeBSD documentation and/or release information:

"Removed the obsolete binutils 2.17 and gcc(1) 4.2.1 from the tree. All
supported architectures now use the LLVM/clang toolchain. 0ad202f312f6,
a04ec978b369, 57f804675e65, 90b9aa475e9e (Sponsored by The FreeBSD
Foundation)"

Therefore please update compilation instructions for FreeBSD for future
PostgreSQL versions by replacing "gcc" with "cc" and changing version
information from FreeBSD 3.0 to 13.0.

Thank you.