MDEV-34825 FreeBSD fails to build under clang natively (postfix)

10.5 added contents of cmake/os/FreeBSD.cmake in c991efd9.
in the merge to 10.11, d002b1f5 removed this file.

In the past FreeBSD.cmake was removed in 5369df74
in the 10.11 branch as no remaining code was needed. The combination
of this and the merge lead to the the file being removed. My assumption is
this was a non-stable branch at the time.

The purpose of this patch is clang doesn't have /usr/local/lib in
the path. As such there are various depedency linkages that will fail.

For example pcre and libfmt.

cmake/os/FreeBSD.cmake

+# Copyright (C) 2024 MariaDB Foundation
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1335  USA 
+
+# This file includes FreeBSD specific options and quirks, related to system checks
+
+# For all userspace dependencies
+LINK_DIRECTORIES(/usr/local/lib)