Creating a gem which installs files outside /usr/lib/ruby

I want to create a gem for an application written using the ruby KDE
bindings.
It’s the first time I create a gem, but I think I more or less
understand what
I should do. The only issue I’m having is that, KDE expects to find some
files
(in particular, the program icon and the program .desktop file) in some
specific directory (namely, in one of the directories listed in the
KDEDIRS
environment variables, which usually means something like /usr/,
/usr/local
and /usr/kde). Is there a way to tell rubygems to install something
outside
the /usr/lib/ruby directory tree? According to the documentation at
http://docs.rubygems.org, rubygems can be told to install binaries in
/usr/bin, but there’s nothing about doing the same for other kind of
files (at
least, I couldn’t find it), so I guess the answer is no.

By the way, the documentation at http://docs.rubygems.org seems quite
outdated
(at least, the Gemspec reference page says it’s last been generated in
2005).
Does anybody know whether more recent documentation can be found?

Thanks in advance

Stefano