Support new-style Dockerfile

[lu-zero]

Docker supports now multi-stage

• Create a compilation stage that takes the image used by cross, copy the source codes, and then runs cargo build --release --target x86_64-unknown-linux-musl to compile the binary
• Create the final image using the compilation artifacts produced in a second stage (as it is right now)

Example for amd-64:

FROM cross-image
COPY src/ Cargo.toml /
RUN cargo build --release --target x86_64-unknown-linux-musl
RUN mkdir -p x86_64-unknown-linux-musl
RUN cp target/x86_64-unknown-linux-musl/release/{{ name }} x86_64-unknown-linux-musl/

FROM amd64/alpine
ADD {{ name }} /
ENTRYPOINT ["/{{ name }}"]

This new approach should remove this part

Docker also supports multi-platform images.

The idea would be to remove the two Dockerfiles present in template, providing a single image that can run on more platforms.