Add dockerfile for cross.

This uses the official Docker docker-in-docker image for the latest
stable, and installs the latest stable Rust version internally. It uses
an entrypoint to ensure cargo is on the path, and that cross is
installed from the latest git (locked), which when tagged will work well
with our releases. It exports the environment variable
`CROSS_CONTAINER_IN_CONTAINER` so everything should work as expected.

Replaces #667.

.github/workflows/ci.yml

@@ -205,6 +205,22 @@ jobs:
             - { target: thumbv7em-none-eabihf,            os: ubuntu-latest,                    std: 1 }
             - { target: thumbv7m-none-eabi,               os: ubuntu-latest,                    std: 1 }
 
+  build-cross:
+    name: Build Cross
+    runs-on: ubuntu-latest
+    needs: [shellcheck, test, generate-matrix, check]
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ./.github/actions/setup-rust
+
+      - name: Build xtask
+        run: cargo build -p xtask
+
+      - name: Build Docker image
+        id: build-docker-image
+        timeout-minutes: 15
+        run: cargo xtask build-docker-image cross
+
   build:
     name: target (${{ matrix.pretty }},${{ matrix.os }})
     runs-on: ${{ matrix.os }}
@@ -309,7 +325,7 @@ jobs:
         shell: bash
 
   publish:
-    needs: [build, check]
+    needs: [build, check, build-cross]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3

CHANGELOG.md

@@ -7,6 +7,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased] - ReleaseDate
 
+### Added
+
+- #878 - added a dockerfile containing cross.
+
 ### Changed
 
 - #869 - ensure cargo configuration environment variable flags are passed to the docker container.

docker/Dockerfile.cross

@@ -0,0 +1,11 @@
+FROM docker:20.10-dind
+
+RUN apk add curl bash libgcc gcc musl-dev git
+
+RUN curl --proto "=https" --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+# need to ensure cargo is in the path when we run this command,
+# since we won't be sourcing the profile.
+RUN PATH="$HOME/.cargo/bin:$PATH" cargo install cross --git https://github.com/cross-rs/cross --locked
+
+COPY cross-entry.sh /
+ENTRYPOINT ["/cross-entry.sh"]

docker/cross-entry.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+# shellcheck disable=SC1090
+. ~/.cargo/env
+export CROSS_CONTAINER_IN_CONTAINER=1
+
+exec "${@}"

docker/cross.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+main() {
+    apk add gcc curl musl-dev
+
+    curl --proto "=https" --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+    PATH="$HOME/.cargo/bin:$PATH" cargo install cross --git https://github.com/cross-rs/cross --locked
+
+    apk del gcc curl musl-dev
+
+    rm -rf "${0}"
+}
+
+main "${@}"