message: Create dummy src file to prevent warning regarding empty library target
diff: +# Create dummy file since we want an empty shared library before linking
  +set(DUMMY_SOURCE ${CMAKE_BINARY_DIR}/dummy.c)
  +file(WRITE ${DUMMY_SOURCE} "")
  +
  # Setup a library with all the common content
  -add_library(spectrecoin_lib)
  +add_library(spectrecoin_lib ${DUMMY_SOURCE})
  # This is the UI wallet
  add_executable(Spectrecoin ../spectre.qrc ${CMAKE_CURRENT_LIST_DIR}/main.cpp)
  