KiCad/kicad-source-mirror — reverse-engineered prompt

I want this repo set up so I can build and run KiCad from source on my machine without having to figure out the whole toolchain myself. Please get the app compiling cleanly, wire up whatever build configuration and dependencies are needed, and make sure the main programs actually launch, especially the project manager, schematic editor, PCB editor, gerber viewer, 3D viewer, page layout editor, and the PCB calculator. If there are demo projects or sample resources in the repo, use those for a basic smoke test so I know the build is really usable.

Please keep the repo structure intact, document the exact steps to build and run it, and add any small helper scripts or notes that make repeat builds easier. If there are platform specific gotchas, call them out clearly. Use the official KiCad developer build docs and current online references if needed, since this looks like the active development mirror and I want the setup to match how the project is supposed to be built now.