Incorrect build instructions

[mpisat]

cd FFmpeg-n4.3.3/metartc6/metartc6
cd libmetartccore6
mkdir build
cd build
./cmake_x64.sh
or
./cmake_android.sh
cp ./libmetartccore6.a ../../

It should be this:

cd FFmpeg-n4.3.3/metartc6/metartc6
cd libmetartccore6
./cmake_x64.sh
or
./cmake_android.sh
cp ./build/libmetartccore6.a /usr/local/lib

Otherwise, ffmpeg can't build due to lack of libmetartccore6.a inside ldconfig folders
For debian 10, those are (default)
/usr/lib/x86_64-linux-gnu/libfakeroot
/usr/local/lib
/usr/local/lib/x86_64-linux-gnu
/lib/x86_64-linux-gnu
/usr/lib/x86_64-linux-gnu