function(list_append var)
foreach(arg ${ARGN})
list(FIND ${var} ${arg} found)
if(${found} EQUAL -1)
list(APPEND ${var} ${arg})
endif()
endforeach()
set(${var} ${${var}} PARENT_SCOPE)
endfunction()
function(list_remove var)
foreach(arg ${ARGN})
list(FIND ${var} ${arg} found)
if(${found} GREATER -1)
list(REMOVE_ITEM ${var} ${arg})
endif()
endforeach()
set(${var} ${${var}} PARENT_SCOPE)
endfunction()