CMake Error at external/CMakeLists.txt:42 (add_subdirectory):
  add_subdirectory given source "miniupnp/miniupnpc" which is not an existing
  directory.


CMake Error at external/CMakeLists.txt:44 (set_property):
  set_property could not find TARGET libminiupnpc-static.  Perhaps it has not
  yet been created.


CMake Error at external/CMakeLists.txt:48 (set_property):
  set_property could not find TARGET libminiupnpc-static.  Perhaps it has not
  yet been created.