Builder image for workflows

.forgejo/workflows/builder-image/Dockerfile

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+FROM rust:latest
+RUN cargo install cross
+
+# This is necessary for cross to be able to access /var/run/docker.sock
+COPY --from=docker:dind /usr/local/bin/docker /usr/local/bin/
+
+RUN curl -fsSL https://deb.nodesource.com/setup_20.x -o nodesource_setup.sh && bash nodesource_setup.sh && rm -f nodesource_setup.sh && apt -y install nodejs && apt clean

.forgejo/workflows/builder-image/build-and-push.sh

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+#!/bin/sh
+#
+# You need to have already logged in:
+#
+#     docker login git.syndicate-lang.org
+#
+# Use a token with read-only access to user scope, this seems to be sufficient (!)
+
+set -e
+docker build -t git.syndicate-lang.org/syndicate-lang/rust-builder .
+docker push git.syndicate-lang.org/syndicate-lang/rust-builder