[CMake] Don't output twice that we generate Doxyfile.in.

It is already printed as the comment of the custom command.

cmake/modules/DuneDoxygen.cmake

@@ -29,7 +29,8 @@ MACRO (prepare_doxyfile)
   message(STATUS "using ${DOXYSTYLE_FILE} to create doxystyle file")
   set(make_doxyfile_command ${CMAKE_COMMAND} -D DOT_TRUE=${DOT_TRUE} -D DUNEWEB_TRUE=\# -D ProjectName=${ProjectName} -D DUNE_MOD_VERSION=${DUNE_MOD_VERSION} -D DOXYSTYLE=${DOXYSTYLE_FILE}  -D DOXYLOCAL=${CMAKE_CURRENT_SOURCE_DIR}/Doxylocal -D abs_top_srcdir=${CMAKE_SOURCE_DIR} -D srcdir=${CMAKE_CURRENT_SOURCE_DIR} -D top_srcdir=${CMAKE_SOURCE_DIR} -P ${SCRIPT_DIR}/CreateDoxyFile.cmake)
   add_custom_command (OUTPUT Doxyfile.in Doxyfile
-    COMMAND ${make_doxyfile_command} COMMENT "Creating Doxyfile.in"
+    COMMAND ${make_doxyfile_command}
+    COMMENT "Creating Doxyfile.in"
     DEPENDS ${DOXYSTYLE_FILE} ${CMAKE_CURRENT_SOURCE_DIR}/Doxylocal)
   add_custom_target(Doxyfile DEPENDS Doxyfile.in Doxyfile)
 ENDMACRO (prepare_doxyfile)

cmake/scripts/CreateDoxyFile.cmake

 #For now we just support appending Doxyfile and Doxylocal
-message(STATUS "Generating Doxyfile.in")
 FILE(READ ${DOXYSTYLE} file_contents)
 FILE(WRITE Doxyfile.in ${file_contents})
 FILE(READ ${DOXYLOCAL} file_contents)