clang is the default compiler on FreeBSD 10 (if not earlier).
Let's keep it unsupported for now. Can be promoted later.
Change-Id: I909953c986a3da09ce19d8f9f9ee2cc22c417abd
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
