In the old buildsystem, installed libraries were checked to see whether parts could be built.
Therefore, it was possible to build only the vision parts, or only the modbus parts etc. Now all libraries are needed to generate the MakeFile.
Some libraries that could be checked during the cmake phase are libmodbus, libmongo, libzbar.
NOTE: this feature is an enhancement request, it is really nice, but only implement this if someone has time left.