Need Clang >= 7 to compile Filament from source

sudo apt-get install -y clang-7

Follow the instruction to install the requirements of the open3d library here 
http://www.open3d.org/docs/release/arm.html#install-dependencies 

Here is what the above code is Doing:
1. Installing the dependencies of the open3d library
2. Installing the clang-7 compiler
3. Installing the open3d library