libheif: Generate pkgconfig file with autoconf
libheif: Generate pkgconfig file with autoconf

Build pkgconfig file using autoconf because
CMake generates it without ${prefix} variable
lhmouse/MINGW-packages,Alexpux/MINGW-packages,Alexpux/MINGW-packages,lhmouse/MINGW-packages,Chocobo1/MINGW-packages,Ede123/MINGW-packages,Ede123/MINGW-packages,oscarfv/MINGW-packages,JPeterMugaas/MINGW-packages,fabiangreffrath/MINGW-packages,stahta01/MINGW-packages,oroppas/MINGW-packages,oroppas/MINGW-packages,stahta01/MINGW-packages,JPeterMugaas/MINGW-packages,Alexpux/MINGW-packages,Chocobo1/MINGW-packages,oscarfv/MINGW-packages,InitialForce/MINGW-packages,InitialForce/MINGW-packages,JPeterMugaas/MINGW-packages,fabiangreffrath/MINGW-packages,lhmouse/MINGW-packages,fabiangreffrath/MINGW-packages,InitialForce/MINGW-packages,lhmouse/MINGW-packages,oscarfv/MINGW-packages,JPeterMugaas/MINGW-packages,Ede123/MINGW-packages,oroppas/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,oroppas/MINGW-packages,oroppas/MINGW-packages,Chocobo1/MINGW-packages,lhmouse/MINGW-packages,stahta01/MINGW-packages,Alexpux/MINGW-packages,Ede123/MINGW-packages,JPeterMugaas/MINGW-packages,Alexpux/MINGW-packages,stahta01/MINGW-packages,Alexpux/MINGW-packages,lhmouse/MINGW-packages,fabiangreffrath/MINGW-packages,JPeterMugaas/MINGW-packages,oscarfv/MINGW-packages,fabiangreffrath/MINGW-packages,stahta01/MINGW-packages,oroppas/MINGW-packages,oscarfv/MINGW-packages,fabiangreffrath/MINGW-packages