Add ROOTSYS env var to release setup script
We've had a request for the ROOTSYS environment variable to point at the release location when the release is setup. I think this seems like a reasonable request. @zewolffs can you perhaps ask Attila how to add such an environment variable to the auto-generated env_setup_install.sh script? I could see a way to hack it into the setup.sh.in in the atlasexternals module but I suspect that isn't necessarily the right place for it to go and instead it should become part of the generated env_setup_install.sh of the release.
Thanks!