quad: add script to build Xilinx project from command line

Problem

It'd be nice to work remotely, without requiring the bandwidth of a GUI.

Solution

Implement a script that executes the build process of the Xilinx SDK.

To build the project, in quad/sw/modular_quad_pid, execute:

./build.sh

Bonus

This was essentially the last piece needed to run a full-build of our Xilinx project on our CI. So it was added.