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.