That fixed it, thank you!
The build finishes without any errors but when I try to run the example "vehicular-simple-one.cc"(the example millicar came with), I get the following error:
msg="Could not set default value for ns3::MmWaveVehicularHelper::SchedulingPatternOption", file=/home/aamina/ns3-mmwave/src/core/model/config.cc, line=899
NS_FATAL, terminating
terminate called without an active exception
Command 'build/src/millicar/examples/ns3.42-vehicular-simple-one-debug' died with <Signals.SIGABRT: 6>.
Again, thank you for all your help till now, truly. You've saved me literal days of having to figure this out on my own.