Improve user story for creating a image/package with the cross compiled binary

[Emilgardis]

Checklist

• I've looked through the issues and pull requests for similar request
• This feature could be solved with a custom docker image (optional)

Describe your request

We should provide a good story for doing something like

FROM magic_cross as cross
COPY . .
RUN cross build --release --target aarch64-unknown-linux-gnu

FROM ubuntu:20.04
COPY --from=cross ./target/release/binary .
CMD ["./binary"]

Describe why this would be a good inclusion for cross

This would make it easy to setup a dockerfile with the needed binary.

Today, this can be solved with

FROM ubuntu:20.04

COPY ./target/aarch64-unknown-linux-gnu/release/binary ./
CMD ["./binary"]

$ cross build --target aarch64-unknown-linux-gnu 
   Compiling binary v0.1.0 (/binary)
    Finished release [optimized] target(s) in 11.68s
$ docker build .
[+] Building 3.0s (7/7) FINISHED                                                                                                                                                                                     
 => [internal] load build definition from Dockerfile                                                                                                                                                            0.0s
 => => transferring dockerfile: 144B                                                                                                                                                                            0.0s
 => [internal] load .dockerignore                                                                                                                                                                               0.0s
 => => transferring context: 2B                                                                                                                                                                                 0.0s
 => [internal] load metadata for docker.io/library/ubuntu:20.04                                                                                                                                                 0.5s
 => [internal] load build context                                                                                                                                                                               0.1s
 => => transferring context: 4.32MB                                                                                                                                                                             0.1s
 => [1/2] FROM docker.io/library/ubuntu:20.04@sha256:0e0402cd13f68137edb0266e1d2c682f217814420f2d43d300ed8f65479b14fb                                                                                           2.3s
 => => resolve docker.io/library/ubuntu:20.04@sha256:0e0402cd13f68137edb0266e1d2c682f217814420f2d43d300ed8f65479b14fb                                                                                           0.0s
 => => sha256:0e0402cd13f68137edb0266e1d2c682f217814420f2d43d300ed8f65479b14fb 1.42kB / 1.42kB                                                                                                                  0.0s
 => => sha256:bfd9523988a26a8913fbced7d00b00805572d093c4d8cbc64252b45e032302d5 529B / 529B                                                                                                                      0.0s
 => => sha256:43ed104e759f96978d95473568dbaef829695dbade5c10be56f344948ab0caa1 1.48kB / 1.48kB                                                                                                                  0.0s
 => => sha256:f04b4bbe15805316c8fda79beedd3b77e6b1ffcd0acf81226c3089e63f6bffeb 27.19MB / 27.19MB                                                                                                                1.3s
 => => extracting sha256:f04b4bbe15805316c8fda79beedd3b77e6b1ffcd0acf81226c3089e63f6bffeb                                                                                                                       0.8s
 => [2/2] COPY ./target/aarch64-unknown-linux-gnu/release/binary ./                                                                                                                                         0.1s
 => exporting to image                                                                                                                                                                                          0.0s
 => => exporting layers                                                                                                                                                                                         0.0s
 => => writing image sha256:d45f5b6b5a01fbe01b3fe6d18a9b124c1586c0905ed92012bf3eb65dd18ae2b1    

Related

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matrix discussion

[Emilgardis]

The best solution would be

FROM ghcr.io/cross-rs/cross:edge as build
WORKDIR /build
COPY . .
RUN cross build --release --target aarch64-unknown-linux-gnu

FROM ubuntu:20.04

COPY --from=build ./target/release/binary ./
CMD ["./binary"]

and invoked with docker build -v /var/run/docker.sock:/var/run/docker.sock ., but docker build can't take a -v, and VOLUME binds at run time.

Technically, I think we could probably use CROSS_REMOTE with DOCKER_CONTEXT=tcp://host.docker.internal:2375 for this, but that seems like a bad idea