No build instructions.

[JNissi]

This needs a little bit of thought.

For cross compilation, install cargo cross, build a docker image for the cross compilation with instructions from cross-rs/cross#517 and richardanaya/pinephone-gtk-rs-starter#4

I needed these on top of Ubuntu 20.04 cargo cross image:

RUN dpkg --add-architecture arm64 && \
    apt-get update && \
    apt-get install --assume-yes libgtk-3-dev:arm64 x11proto-dev:arm64 libssl-dev:arm64 libasound2-dev:arm64 libpulse-dev:arm64 -o APT::Immediate-Configure=0 && \
    apt-get install -y clang libclang-3.9-dev libc6-dev-i386 gcc-aarch64-linux-gnu && \
    apt-get clean -y

ENV PKG_CONFIG_LIBDIR=/usr/local/lib/aarch64-linux-gnu/pkgconfig:/usr/lib/aarch64-linux-gnu/pkgconfig:/usr/share/pkgconfig/
ENV PKG_CONFIG_ALLOW_CROSS=1

When the docker image is built change the image name in Cross.toml and do
cross build --target aarch64-unknown-linux-gnu --release and copy target/aarch64-unknown-linux-gnu/release/camcam to the phone.