THRIFT-3106 CMake summary should give more information why a library is set to off

Patch: Pascal Bach
This closes #454
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 386a63d..70bdb75 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -72,7 +72,7 @@
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/compiler/cpp)
 endif()
 
-if(WITH_CPP)
+if(BUILD_CPP)
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/lib/cpp)
     if(BUILD_TESTING)
         if(WITH_LIBEVENT AND WITH_ZLIB AND WITH_OPENSSL)
@@ -83,15 +83,15 @@
     endif()
 endif()
 
-if(WITH_C_GLIB)
+if(BUILD_C_GLIB)
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/lib/c_glib)
 endif()
 
-if(WITH_JAVA)
+if(BUILD_JAVA)
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/lib/java)
 endif()
 
-if(WITH_PYTHON)
+if(BUILD_PYTHON)
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/lib/py)
 endif()