Quick start: I think make -j is not a good idea

I don't think "make -j" should be recommended in the quick start guide. I just ran this on a moderately resourced VM (4 cores, 8 GB memory) and it ran the VM out of memory, leaving it inaccessible by SSH, probably because the SSH server got starved. I logged in through VMware Workstation and was able to see that there were dozens of cc1plus processes running. "make -j nproc" would be safer I think.

https://grpc.io/docs/languages/cpp/quickstart/