mingw-runtime: Don't copy pkg-config on top of itself
mingw-runtime: Don't copy pkg-config on top of itself

Obviously we shouldn't try to copy pkg-config from the build tools
prefix when our current prefix is the build tools prefix...

https://gitlab.freedesktop.org/gstreamer/cerbero/merge_requests/83#note_107479

fluendo/cerbero,fluendo/cerbero,atsushieno/cerbero,nirbheek/cerbero,fluendo/cerbero,atsushieno/cerbero,GStreamer/cerbero,atsushieno/cerbero,GStreamer/cerbero,GStreamer/cerbero,atsushieno/cerbero,GStreamer/cerbero,fluendo/cerbero,nirbheek/cerbero,fluendo/cerbero,nirbheek/cerbero,nirbheek/cerbero,atsushieno/cerbero,GStreamer/cerbero