We need them when building gir and typelib files for libraries that depend on these, such as gst-rtsp-server for example, in an uninstalled setup.
Original commit message from CVS: * configure.ac: * pkgconfig/Makefile.am: * pkgconfig/gstreamer-app-uninstalled.pc.in: * pkgconfig/gstreamer-app.pc.in: Add pkg-config files for libgstapp. Fixes bug #566761.