Paulo Penteado has updated his Building cross-platform IDL runtime applications article with an über-installation for IDL 8.3 on all current platforms:

I created a package for IDL 8.3. It contains all the files in the current manifest_rt.txt file, which cover all the current platforms: Linux (x86_64), Windows (x86 and x86_64), Mac (x86_64) and Solaris (x86_64 and sparc64).

The über-installation (download) allows MAKE_RT to make all-inclusive IDL runtime applications that work on all platforms.