This patch adds a new flag --separate_servers to indicate whether to build
pegasus_collector，pegasus_meta_server and pegasus_replica_server binaries
separately, otherwise a combined pegasus_server binary will be built. The
corresponding option in CMake is SEPARATE_SERVERS.
This patch adds a new flag
--separate_serversto indicate whether to buildpegasus_collector，pegasus_meta_serverandpegasus_replica_serverbinaries separately, otherwise a combinedpegasus_serverbinary will be built. The corresponding option in CMake isSEPARATE_SERVERS.