Symbolic links on Windows require some special user privilege, and
Shaman can now check for this at startup. Hopefully this helps in guiding
people towards a working Shaman system.
In addition to logging `GOOS` and `GOARCH`, also log more info about the
system:
- Windows: the Windows version and edition.
- Linux: distribution, distribution version, and kernel version.
- macOS: just "macOS", until we know more about getting info there too.
