[PATCH rtems-docs] posix.rst: Add info for FreeBSD 13

[Ryan Long]

Add list of additional packages needed to build RTEMS environment for
FreeBSD 13.
---
 user/hosts/posix.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/user/hosts/posix.rst b/user/hosts/posix.rst
index 6686fc9..284df48 100644
--- a/user/hosts/posix.rst
+++ b/user/hosts/posix.rst
@@ -195,6 +195,16 @@ The RTEMS Source Builder has been tested on FreeBSD 9.1, 10.3, 11 and
   # pkg install -y python
   # pkg install -y gsed
 
+For FreeBSD 13, you will need to install the packages listed above, as well as
+the following additional ones. They are:
+
+.. code-block:: none
+
+  # pkg install -y bison
+  # pkg install -y texinfo
+  # pkg install -y gmake
+  # pkg install -y binutils
+
 FreeBSD's default C compiler is LLVM and installing the host's GCC compiler
 package may break building GCC. We recommend you do not install the GCC
 package and you use the default C compiler.
-- 
1.8.3.1