Build scripts that eval a user setup command: guard set -u and stdin

If a build or remote script runs a user-supplied environment setup string (e.g. eval "$TOOL_SETUP" for module load or vendor env scripts), three failures hide easily. (1) Under set -u, any unset variable inside the setup aborts it; if stderr is hidden, the user only sees a later 'tool not found'. Run it as ( set +u; eval "$SETUP" </dev/null ) with a timeout. (2) A script fed over ssh on stdin gets swallowed by a setup that reads stdin, so redirect </dev/null. (3) Non-login sh -c never reads the login profile, so telling users to put the setup in their profile doesn't work. Test from a plain non-login sh on the target host before shipping.