Add internal DNS server if no custom DNS is set (#45)

Fixes #44

Co-authored-by: Lauris BH <lauris@nix.lv>
Reviewed-on: https://codeberg.org/woodpecker-plugins/plugin-docker-buildx/pulls/45
Reviewed-by: 6543 <6543@obermui.de>
Co-authored-by: Lauris BH <lafriks@noreply.codeberg.org>
Co-committed-by: Lauris BH <lafriks@noreply.codeberg.org>

Dockerfile.multiarch

@@ -15,6 +15,9 @@ RUN --mount=type=cache,target=/root/.cache/go-build \
 FROM docker/buildx-bin:${BUILDX_VERSION} as buildx-bin
 FROM docker:${DOCKER_VERSION}
 
+RUN apk --update --no-cache add coredns
+
+COPY --from=build /src/Corefile /etc/coredns/Corefile
 COPY --from=buildx-bin /buildx /usr/libexec/docker/cli-plugins/docker-buildx
 COPY --from=build /src/plugin-docker-buildx /bin/plugin-docker-buildx