So, if one wants to build one group and only those files installed, MODULE_GROUP_NAME should only contain ONE group name, ie MODULE_GROUP_NAME=KSTANDARD in the configuration phase. Afterwards, build and installed will install only that group!
This flow doesn't work at all. If you call just one group, core gets build for that group. And in combination of different build dir for each group... You end up building the core for each group again and again.