ffmpeg: Add pkgconfig static flag for static library
ffmpeg: Add pkgconfig static flag for static library

Also remove celt library which is not in development and provided by opus.
stahta01/MINGW-packages,JPeterMugaas/MINGW-packages,JPeterMugaas/MINGW-packages,Alexpux/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,Alexpux/MINGW-packages,oscarfv/MINGW-packages,oscarfv/MINGW-packages,oroppas/MINGW-packages,JPeterMugaas/MINGW-packages,oscarfv/MINGW-packages,fabiangreffrath/MINGW-packages,oroppas/MINGW-packages,lhmouse/MINGW-packages,fabiangreffrath/MINGW-packages,stahta01/MINGW-packages,lhmouse/MINGW-packages,Alexpux/MINGW-packages,stahta01/MINGW-packages,fabiangreffrath/MINGW-packages,fabiangreffrath/MINGW-packages,oscarfv/MINGW-packages,stahta01/MINGW-packages,oroppas/MINGW-packages,Alexpux/MINGW-packages,Alexpux/MINGW-packages,Alexpux/MINGW-packages,lhmouse/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,oroppas/MINGW-packages,lhmouse/MINGW-packages,lhmouse/MINGW-packages,oroppas/MINGW-packages,JPeterMugaas/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,fabiangreffrath/MINGW-packages,JPeterMugaas/MINGW-packages,oroppas/MINGW-packages,fabiangreffrath/MINGW-packages