multiarch to build a linux/x86_64 go_test() on a Darwin/arm64 host ?

hey.

Would you be accepting of a PR that allows the user to run go_docker_compose_test() on an platform_host not matching the container arch?

ie:

go_docker_compose_test(
    name = "go-test-image-test",
    docker_compose_file = ":docker-compose.yml",
    docker_compose_test_container = "test_container",
+ platforms =  platforms = [ ":linux_arm64", ":linux_amd64" ],  # Mac and linux both run GOOS==linux
    test_srcs = glob(["**/*_test.go"]),
    test_deps = [],
    test_image_base = "@ubuntu",
)

...to allow building a multi-arch OCI (index + 2 images), even on a Mac? User-story here would be a Mac user testing linux OCI images locally and wanting to compile that unittest with the proper linux GOOS so that the test-runner runs in the container arch/os.

Alternatively, plumbing through GOOS might suffice, but GOARCH may still depend on the host.

Start at the go_docker_compose_test rule and trace how platform_host, GOOS/GOARCH, and the test container image are currently selected. Determine whether the requested platforms can produce a multi-architecture OCI image index and run tests for the container architecture; done means a Darwin/arm64 host can test the corresponding linux image without mismatched binaries.