build: export dependencies for native integration tests

The Debian development image supplies the Go toolchain, runtime binaries,
test reporter, and frozen images. Even the VM jobs run inside that image,
so these dependencies have not needed to be installed on the guest.

Add a scratch export target that reuses the existing pinned build stages.
Native tests can then compile the daemon and tests against the guest's
userspace while retaining the same tools and fixtures. Export static
runtime binaries so they also work on older guest distributions.

Assisted-by: Codex
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

Dockerfile

@@ -615,6 +615,20 @@ COPY --link --from=rootlesskit   /build/ /
 COPY --link --from=containerutil /build/ /
 COPY --link --from=build         /build  /
 
+# Tools and fixtures for running integration tests directly on a Linux host.
+# Build this for the host architecture; the Go toolchain and gotestsum run there.
+# The daemon and tests are compiled on the host by hack/make.sh.
+FROM scratch AS test-integration-deps
+COPY --link --from=base          /usr/local/go/ /usr/local/go/
+COPY --link --from=tini          /build/ /usr/local/bin/
+COPY --link --from=runc          /build/ /usr/local/bin/
+COPY --link --from=containerd    /build/ /usr/local/bin/
+COPY --link --from=rootlesskit   /build/ /usr/local/bin/
+COPY --link --from=dockercli     /build/ /usr/local/bin/
+COPY --link --from=gotestsum     /build/ /usr/local/bin/
+COPY --link --from=registry      /build/ /usr/local/bin/
+COPY --link --from=frozen-images /build/ /docker-frozen-images/
+
 # smoke tests
 # usage:
 # > docker buildx bake binary-smoketest

docker-bake.hcl

@@ -141,6 +141,16 @@ target "all-cross" {
   inherits = ["all", "_platforms"]
 }
 
+# Export the pinned tools and fixtures for integration tests on a Linux host.
+target "test-integration-deps" {
+  inherits = ["_common"]
+  target = "test-integration-deps"
+  args = {
+    DOCKER_STATIC = "1"
+  }
+  output = [bindir("test-integration-deps")]
+}
+
 #
 # bin image
 #