`make generate` only works on linux

## Description
After #4943 there is new command `generate` as part of the Makefile. But it is currently downloading specifically the linux binaries for protoc and then executing them.

This might also work in WSL I guess, but is unlikely to work on windows outside of it and on MacOS

## Proposal

Have the Makefile correctly choose which versions it should download and unzip for Mac OS and Windows. 