Hello,
got some issues when i build my c++ project that needs some additional libs to be built first.
The usual way and the way it works on my system is, to git clone make and make install the lib first but it always ignores prefix or any other kind of destination switches i can use outside flatpak builder. make install in flatpak gets it wrong and is trying to install in a system path that is not existent inside the flatpak structure.
What is the solution to this? Simply creating the directory won’t solve it, i did try that: mkdir -p /usr/lib/x86_64-linux-gnu
Please help 
Thanks!