travis: include win/darwin binaries in cross

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

.travis.yml

@@ -12,7 +12,7 @@ env:
     - PREFER_BUILDCTL="1"
 
 script:
-  - make binaries validate-all && ./hack/cross
+  - make binaries validate-all && PLATFORMS="${PLATFORMS},darwin/amd64,windows/amd64" ./hack/cross
 
 before_deploy:
   - echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin

hack/dockerfiles/test.buildkit.Dockerfile

@@ -174,10 +174,15 @@ COPY --from=buildctl /usr/bin/buildctl /usr/bin/
 ENTRYPOINT ["buildkitd.containerd_only"]
 
 # Copy together all binaries for oci+containerd mode
-FROM buildkit-export AS buildkit-buildkitd
+FROM buildkit-export AS buildkit-buildkitd-linux
 COPY --from=binaries / /usr/bin/
 ENTRYPOINT ["buildkitd"]
 
+FROM binaries AS buildkit-buildkitd-darwin
+FROM binaries AS buildkit-buildkitd-windows
+
+FROM buildkit-buildkitd-$TARGETOS AS buildkit-buildkitd
+
 FROM alpine AS containerd-runtime
 COPY --from=runc /usr/bin/runc /usr/bin/
 COPY --from=containerd /out/containerd* /usr/bin/