Add more problems to the list.

qt/readme.txt

@@ -8,6 +8,12 @@ For use of dynamic plugins, it is desirable to build qt with -shared, but
 other problems exist with OpenPKG gcc-3.1-* on all platforms. Therefore qt
 builds with -static now. See the last bunch of error messages for details.
 
+Lastly, the resulting qt package seems to work fine. However, subsequent
+package upgrades fail to build. The workaround is to deinstall the qt package
+from an OpenPKG instance before trying to build a newer version. I don't know
+what is causing this problem and unfortunately Trolltech has its own build
+standard, making it even harder to troubleshoot.
+
                                     - Michael Schloh von Bennewitz
 
 -------- First problem building with -system-libpng