Well, after some digging, I finally found some old posts from someone facing the same problem. It turns out that, apparently, the Madde tools provided for the N900 (in the 4.6.2 version of the Qt Maemo toolchain) have a few bugs. In particular, the xdpkg / dpkg scripts do not properly generate or look for "shlibs" files when installing / using a new library package. Fixing this apparently involves grabbing the latest copy of xdpkg off the gitorious site:

https://meego.gitorious.org/meego-de...adlib/xdpkg.pl

and using it to replace the xdpkg script in the Qt SDK directory Maemo/4.6.2/madlib/ma-cmds, as well as replacing the "dpkg" and "dh_shlibdeps" scripts under Maemo/4.6.2/madbin with those found in the Madde/madbin directory.

Here are some links to discussions of this bug:

http://maemo.org/community/maemo-dev...maemo_sysroot/

http://qt-project.org/forums/viewthread/9253

I have to admit, this only worked partially for me; the new scripts did successfully create a .shilibs file for the libqjson0 package (under the directory $SYSROOT/madde_xpkgs), but apparently still didn't look in that directory when trying to build against the library. However, I know that it does look in the $SYSROOT/var/lib/dpkg/info directory for shlib files, so for now, I went ahead and copied the libqjson0 files into that directory. And that worked!

So now, I can at least build and run against libqjson0. Hooray!