message: Make headers private sources
  Otherwise they get added to Editor and Player when they use a local
  liblcf.
  Related EasyRPG/Editor#172
diff: @@ -313,7 +313,7 @@ list(TRANSFORM LCF_SOURCES PREPEND ${CMAKE_CURRENT_SOURCE_DIR}/)
  list(TRANSFORM LCF_HEADERS PREPEND ${CMAKE_CURRENT_SOURCE_DIR}/)
  list(APPEND LCF_HEADERS ${CMAKE_CURRENT_BINARY_DIR}/src/lcf/config.h)
  -target_sources(lcf PRIVATE ${LCF_SOURCES} PUBLIC ${LCF_HEADERS})
  +target_sources(lcf PRIVATE ${LCF_SOURCES} ${LCF_HEADERS})
  # IDE source grouping
  foreach(SG LDB LMT LMU LSD RPG THIRD_PARTY)
  