Usage: set_ccopt_property buffer_cells <value>:
Specifies the buffer cells for CTS. If none are specified CCOpt will choose buffers from the libraries.
Cell names may be specified as a Tcl list of names, or as a Tcl list of patterns to be expanded to match names.
If set explicitly, CCOpt will ignore any don't use settings for the cells specified. <- 这句是关键