message: check for msgpack during source configure
diff: @@ -36,6 +36,13 @@ file(TO_CMAKE_PATH ${JANSSON_LIB_DIR} JANSSON_LIB_DIR)
  include(CheckLibraryExists)
  check_library_exists(jansson json_dumps "${JANSSON_LIB_DIR}" HAVE_JANSSON)
  +# check msgpack is available in the source tree
  +set(msgpackfile "${PROJECT_SOURCE_DIR}/external/msgpack-c/include/msgpack.h")
  +message(STATUS "checking for ${msgpackfile}")
  +if(NOT EXISTS "${msgpackfile}")
  + message(FATAL_ERROR "msgpack header not found! Check msgpack unzipped under external/")
  +endif()
  +
  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/config.h.cmake ${CMAKE_CURRENT_BINARY_DIR}/config.h)
  ## Paths
  