PR #6593 broke activation when `sessionVariablesExtra` is used, e.g.:
`services.ssh-agent` because it concatenate the strings without a line
break, so the resulting `hm-session-vars.sh` file became:
```bash
export XCURSOR_PATH="/etc/profiles/per-user/thiagoko/share/icons${XCURSOR_PATH:+:}$XCURSOR_PATH"if [ -z "$SSH_AUTH_SOCK" ]; then
export SSH_AUTH_SOCK=$XDG_RUNTIME_DIR/ssh-agent
fi
```
This commit fixes it by enforcing a line break between
`sessionSearchVariables` and `sessionVariablesExtra`.
db4386d686