Tests/RunCMake/CMP0171/CMP0171-WARN.cmake - external/github.com/Kitware/CMake - Git at Google

 # CMake should warn the user if they have a target named codegen.
 add_custom_target(codegen
   COMMAND ${CMAKE_COMMAND} -E copy
     ${CMAKE_CURRENT_SOURCE_DIR}/generated.h.in
     ${CMAKE_CURRENT_BINARY_DIR}/generated.h
 )
	# CMake should warn the user if they have a target named codegen.
	add_custom_target(codegen
	COMMAND ${CMAKE_COMMAND} -E copy
	${CMAKE_CURRENT_SOURCE_DIR}/generated.h.in
	${CMAKE_CURRENT_BINARY_DIR}/generated.h
	)