I also modified the CMake and pkgconfig files to append the _POSTFIX extenstion based on the CMAKE_BUILD_TYPE.
Additionally I fixed packaging/ld.so.conf.d/openscenegraph.conf.in to add a '/' betweeen the arguments since the CMAKE_INSTALL_PREFIX can't end with a '/'.
"
1. Install the .pc file for osgIntrospection only if it is compiled,
instead of unconditionally.
2. New .pc file for osgQt, also created only if that library is actually
compiled.
"