Do not convert file everytime it is configured

Author: leolchat

CMakeLists.txt

@@ -126,7 +126,7 @@ FOREACH (F ${PREDEF_FILES})
    FILE (READ ${CMAKE_CURRENT_SOURCE_DIR}/external/boost/predef/include/boost/${F} CONTENT)
    STRING(REPLACE "BOOST_" "MSGPACK_" CONTENT ${CONTENT})
    STRING(REPLACE "boost/" "msgpack/" CONTENT ${CONTENT})
-   FILE (WRITE ${CMAKE_CURRENT_SOURCE_DIR}/include/msgpack/${F} ${CONTENT})
+   FILE (GENERATE OUTPUT ${CMAKE_CURRENT_SOURCE_DIR}/include/msgpack/${F} CONTENT ${CONTENT})
 ENDFOREACH ()
 
 FILE (GLOB_RECURSE PREPROCESSOR_FILES RELATIVE ${CMAKE_CURRENT_SOURCE_DIR}/external/boost/preprocessor/include/boost ${CMAKE_CURRENT_SOURCE_DIR}/external/boost/preprocessor/include/boost/*.hpp)
@@ -136,7 +136,7 @@ FOREACH (F ${PREPROCESSOR_FILES})
    FILE (READ ${CMAKE_CURRENT_SOURCE_DIR}/external/boost/preprocessor/include/boost/${F} CONTENT)
    STRING(REPLACE "BOOST_" "MSGPACK_" CONTENT ${CONTENT})
    STRING(REPLACE "boost/" "msgpack/" CONTENT ${CONTENT})
-   FILE (WRITE ${CMAKE_CURRENT_SOURCE_DIR}/include/msgpack/${F} ${CONTENT})
+   FILE (GENERATE OUTPUT ${CMAKE_CURRENT_SOURCE_DIR}/include/msgpack/${F} CONTENT ${CONTENT})
 ENDFOREACH ()
 
 FIND_PACKAGE (GTest)