[CMakeLists] update with cppadcg example

Author: proyan

example/CMakeLists.txt

@@ -1,2 +1,4 @@
 ADD_PYTHON_UNIT_TEST("add_eq" "example/add_eq.py" "python")
-ADD_PYTHON_UNIT_TEST("cppad_type" "example/cppad_type.py" "python")
+IF(BUILD_WITH_CPPAD_CODEGEN_BINDINGS)
+  ADD_PYTHON_UNIT_TEST("cppadcg_c_codegen" "example/cppadcg_c_codegen.py" "python")
+ENDIF(BUILD_WITH_CPPAD_CODEGEN_BINDINGS)