rework script to create loki installer

the script now automatically picks up the architectures present in
the build directory. Also builds installer without data files if no
data files are present.

Wrt loki metadata the installer now installs ioq3 as default
component instead of the data files. After all baseq3 is just a mod
(almost) like any other.

misc/setup/preuninstall.sh

@@ -1,3 +1,2 @@
 #!/bin/sh
-rm -f COPYING
 rmdir --ignore-fail-on-non-empty demoq3 missionpack >& /dev/null