By the way, in all of my Trinity builds I set
LD_LIBRARY_PATH=/opt/trinity/lib:/opt/trinity/lib/trinity. Does that make a difference?
These paths are the ones for the final packages. They should be added to /etc/ld.so.conf, and I think the install script of the package every other one needs (so I suppose it's qt3/tqt3) is a good place to do that. If you choose that way, don't forget to take account of the lib->lib64 transformation when 64-bit packages are built; you can take the Qt3 build script of KDE 3.5.10 for Slackware 13.0 as an example. (for $trinityprefix/lib{,64} your (T)Qt3 build script perhaps already does that)
I am adding /opt/trinity/lib${LIBDIRSUFFIX} to /etc/ld.so.conf, through my TQt3 package.
Darrell