message: Fix a small problem with add_subdirectory(${FLATBUFFERS_DIR}) from top level project.
diff: find_program(GIT git)
  execute_process(
  COMMAND ${GIT} describe
  - WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
  + WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
  OUTPUT_VARIABLE GIT_DESCRIBE_DIRTY
  OUTPUT_STRIP_TRAILING_WHITESPACE
  )
  