ci: Build on windows

[cameron-martin]

This requires a few hacks to avoid hitting the Windows path limit, plus a few generalisations around path names and usage of platform-specific extension traits.

[albertocavalcante]

Hey @cameron-martin, would like help on this one?

[cameron-martin]

Yes please. I believe the problem is that paths of certain files in the runfiles tree exceed the 260 character limit imposed by Windows. I fixed this for the rules_rust bzlmod examples in bazelbuild/rules_rust#2454 by shortening various components of the path, but for some reason the paths here are still exceeding this limit. I'm yet to work out why this is, so help is very much appreciated.

[hauserx]

Added commit to fix failing tests under windows in #55, feel free to cherry-pick that commit to this PR or close the other PR if not useful.

[cameron-martin]

Thanks. I've added your commit to this PR since I had to fix a rust-analyzer issue too. I'll close your PR, but thanks for fixing this issue!

[hauserx]

Could you also add test --test_output=errors to .bazelrc?

Or is it possible to make the buildbuddy links public / accessible (I guess it would should errors for tests as well). I am getting Permission denied for https://bazel-lsp.buildbuddy.io/invocation/5e19d021-dbe4-4a27-86aa-bb04c9cdf2a7

[cameron-martin]

I believe this issue is fixed now, but I've enabled a setting that should make builds public in #58.