macro(AddExternalTarget _VARS)
  set(LST ${ARGV})
  list(GET LST 0 TGT)
  list(REMOVE_AT LST 0)

  foreach(EXT_TGT ${LST})
    if (${EXT_TGT})
      add_dependencies(${TGT} ${${EXT_TGT}})
    endif()
  endforeach() 
endmacro()
