Prefer cc and c++ when using CMake on FreeBSD

As of FreeBSD 10.X, clang is installed as the default compiler with "cc"
and "c++" as aliases to "clang" and "clang++" respectively.

lib/mini_portile2/mini_portile_cmake.rb

@@ -94,6 +94,9 @@ def find_c_and_cxx_compilers(host)
     if MiniPortile.darwin?
       c_compiler ||= 'clang'
       cxx_compiler ||='clang++'
+    elsif MiniPortile.freebsd?
+      c_compiler ||= 'cc'
+      cxx_compiler ||= 'c++'
     else
       c_compiler ||= 'gcc'
       cxx_compiler ||= 'g++'

test/test_cmake.rb

@@ -107,6 +107,37 @@ def test_configure_defaults_with_macos
     end
   end
 
+  def test_configure_defaults_with_freebsd
+    recipe = init_recipe
+    recipe.host = 'some-host'
+
+    with_env({ "CC" => nil, "CXX" => nil }) do
+      MiniPortile.stub(:linux?, false) do
+        MiniPortile.stub(:windows?, false) do
+          MiniPortile.stub(:darwin?, false) do
+            MiniPortile.stub(:freebsd?, true) do
+              with_stubbed_target do
+                with_compilers(recipe, c_compiler: 'cc', cxx_compiler: 'c++') do
+                  Open3.stub(:capture2, cmake_help_mock('Unix')) do
+                    assert_equal(
+                      [
+                        "-DCMAKE_SYSTEM_NAME=FreeBSD",
+                        "-DCMAKE_SYSTEM_PROCESSOR=x86_64",
+                        "-DCMAKE_C_COMPILER=cc",
+                        "-DCMAKE_CXX_COMPILER=c++",
+                        "-DCMAKE_BUILD_TYPE=Release"
+                      ],
+                      recipe.configure_defaults)
+                  end
+                end
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+
   def test_configure_defaults_with_manual_system_name
     recipe = init_recipe
     recipe.system_name = 'Custom'