Generating those files is useful for users building the GStreamer stack
using meson and having to link it to another project which is still
using the autotools.
While doing so, fix some -uninstalled pc files which were using a
suspicious 'pcfiledir' which was never replaced or defined.
https://bugzilla.gnome.org/show_bug.cgi?id=776810
Currently the .la path is provided which requires to use libtool as
mentioned in the GStreamer manual section-helloworld-compilerun.html.
It is fine as long as the application is built using libtool.
So currently it is not possible to compile a GStreamer application
within gst-uninstalled with CMake or other build system different
than autotools.
This patch allows to do the following in gst-uninstalled env:
gcc test.c -o test $(pkg-config --cflags --libs gstreamer-1.0 \
gstreamer-gl-1.0)
Previously it required to prepend libtool --mode=link
https://bugzilla.gnome.org/show_bug.cgi?id=720778
