If the installer is invoked without superuser privileges, warn the user,
ask for the installation prefix, and perform a local installation on
confirmation.
Use tar's --skip-old-files option for the data directory (/opt/ejabberd)
only. Files in the code directory (/opt/ejabberd-$version) should be
overridden on upgrade.
The tools/make-installers script creates command line installers for
Linux/x64 and Linux/arm64 systems using the archives built by the
tools/make-binaries script.