message: Parallelize the builds of dependencies
diff: +include(ProcessorCount)
  +
  function(build_target SRC_DIR TARGET_DIR)
  file(MAKE_DIRECTORY ${TARGET_DIR}/build)
  @@ -18,6 +20,9 @@ function(build_target SRC_DIR TARGET_DIR)
  WORKING_DIRECTORY "${TARGET_DIR}/build"
  )
  + ProcessorCount(NUM_PROCS)
  +
  + set(ENV{MAKEFLAGS} -j${NUM_PROCS})
  execute_process(COMMAND ${CMAKE_COMMAND} --build .
  WORKING_DIRECTORY ${TARGET_DIR}/build
  )
  