cmake: fix variable setting for old cmake versions

CMakeLists.txt

@@ -63,9 +63,15 @@ OPTION(BUILD_WITH_CODEGEN_SUPPORT "Build the library with the Code Generation su
 
 OPTION(INITIALIZE_WITH_NAN "Initialize Eigen entries with NaN" OFF)
 
-SET(BUILD_WITH_HPP_FCL_SUPPORT ${BUILD_WITH_COLLISION_SUPPORT})
-SET(BUILD_WITH_CPPAD_SUPPORT ${BUILD_WITH_AUTODIFF_SUPPORT})
-SET(BUILD_WITH_CPPAD_CODEGEN_SUPPORT ${BUILD_WITH_CODEGEN_SUPPORT})
+IF(BUILD_WITH_COLLISION_SUPPORT)
+  SET(BUILD_WITH_HPP_FCL_SUPPORT TRUE)
+ENDIF()
+IF(BUILD_WITH_AUTODIFF_SUPPORT)
+  SET(BUILD_WITH_CPPAD_SUPPORT TRUE)
+ENDIF()
+IF(BUILD_WITH_CODEGEN_SUPPORT)
+  SET(BUILD_WITH_CPPAD_CODEGEN_SUPPORT TRUE)
+ENDIF()
 
 IF(INITIALIZE_WITH_NAN)
   MESSAGE (STATUS "Initialize with NaN all the Eigen entries.")