MDEV-34825 FreeBSD fails to build under clang natively

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

@@ -28,3 +28,6 @@ SET(EXECINFO_ROOT /usr/local CACHE INTERNAL "Where to find execinfo library and
 INCLUDE_DIRECTORIES(${EXECINFO_ROOT}/include)
 SET(CMAKE_REQUIRED_INCLUDES ${CMAKE_REQUIRED_INCLUDES} ${EXECINFO_ROOT}/include)
 SET(ENV{LIB} "$ENV{LIB}:${EXECINFO_ROOT}/lib")
+
+# For all userspace dependencies
+LINK_DIRECTORIES(/usr/local/lib)