macro to check for different input and output file and if needed replace output file

cMake/FreeCadMacros.cmake

@@ -26,6 +26,26 @@ MACRO (fc_copy_sources target_name outpath)
 	)
 ENDMACRO(fc_copy_sources)
 
+MACRO (fc_copy_file_if_different inputfile outputfile)
+    if (EXISTS ${outputfile})
+        execute_process(
+            COMMAND ${CMAKE_COMMAND} -E compare_files ${inputfile}
+                                                      ${outputfile}
+            RESULT_VARIABLE DIFFERENT_FILES
+            OUTPUT_QUIET
+            ERROR_QUIET
+        )
+
+        if (DIFFERENT_FILES)
+            execute_process(COMMAND "${CMAKE_COMMAND}" -E copy "${inputfile}"
+                                                               "${outputfile}")
+        endif()
+    else()
+        execute_process(COMMAND "${CMAKE_COMMAND}" -E copy "${inputfile}"
+                                                           "${outputfile}")
+    endif()
+ENDMACRO(fc_copy_file_if_different)
+
 MACRO (fc_target_copy_resource target_name inpath outpath)
 # Macro to copy a list of files into a nested directory structure
 # Arguments -