Running the install-rpi.sh script on the Pi takes a long time.

[BaukeWestendorp]

Some things we could do to speed up the script include:

• Only installing the necessary Rust parts
• Try to use less dependencies in Gauge and Carburetor that need to be built. #100
• protocol = "sparse"

[BaukeWestendorp]

We could use the experimental rust-lang/rfcs#2789.

This allows us to use

[registries.crates-io]
protocol = "sparse"

in .cargo/config.toml to prevent loading the entire crates.io index.