As I'm building my little Urho3D based game-server to run on rpi and alike systems I tend to compile the whole stuff on the device itself. (Yeah,...I should have a look in just cross-compiling...). I often struggled to finish compilation due to problems with angelscript and assimp here is the cmake-call to ignore those:
cmake -DURHO3D_ANGELSCRIPT=0 -DURHO3D_SAMPLES=0 -DURHO3D_TOOLS=0 /path/to/urho3dsource