Fix BCR presubmit on windows

[alexeagle]

See https://github.com/bazelbuild/bazel-central-registry/pull/513/files#diff-f32762d4a16f5f26043de312cfaa0b017b1f36ed0b02b52727a810e5daffd76dR4-R8

[alexeagle]

not fixed: https://buildkite.com/bazel/bcr-presubmit/builds/1126#0186dd9f-cbff-4f73-8cfb-d6d96ffa913f
and this is difficult because https://github.com/project-zot/zot/releases doesn't have any windows binaries?

[alexeagle]

@thesayyn could we just not register a zot toolchain in the e2e/smoke? then Windows could be green?

[thesayyn]

not really if we really want it to be a simple smoke test where we assert registry and oci_image works.

[alexeagle]

Seems like there's another Windows bug separate from the above:

[alexeagle]

Update, I think I have fixed all the bugs! Now just waiting on a release of https://github.com/GoogleContainerTools/container-structure-test which @loosebazooka hopes to get to today.

[alexeagle]

With everything put together now, #307 makes it green for me locally on Windows, but I'm struggling with the CI failure on that PR.