Avoid unnecessary library rebuild while still keeping CLion happy.

Source/Urho3D/CMakeLists.txt

@@ -40,7 +40,9 @@ if (WIN32)
 endif ()
 
 # Define generated source files
-execute_process (COMMAND ${CMAKE_COMMAND} -E touch ${CMAKE_CURRENT_BINARY_DIR}/librevision.h)
+if (NOT EXISTS ${CMAKE_CURRENT_BINARY_DIR}/librevision.h)
+    execute_process (COMMAND ${CMAKE_COMMAND} -E touch ${CMAKE_CURRENT_BINARY_DIR}/librevision.h)
+endif ()
 add_custom_command (OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/librevision.h
     COMMAND ${CMAKE_COMMAND} -DFILENAME=${CMAKE_CURRENT_BINARY_DIR}/librevision.h -P CMake/Modules/GetUrho3DRevision.cmake
     DEPENDS ${STATIC_LIBRARY_TARGETS} ${CMAKE_SOURCE_DIR}/CMake/Modules/GetUrho3DRevision.cmake