Generator always fails to find config file on Windows

[jakepetroules]

Description

This is due to the code in PluginUtils.swift which uses $0.path.lastComponent to get the filename of files in a FileList (which is SwiftPM package plugin API).

Unfortunately, path.lastComponent is broken on Windows, but there is a functional replacement url.lastComponent in manifest versions 6.0 or later.

When can swift-openapi-generator adopt 6.0 manifest version, or what can we do to resolve this on Windows?

[czechboy0]

We'll be able to bump the tools version to 6.0 when 6.2 ships, to continue our support window of 3 released Swift versions.

To add Windows support, we'll probably first need to enable Windows CI as a non-required check, and incrementally work through any issues (like this one) to get it to green.

Happy for you to open that PR first if you'd like.

[jakepetroules]

I filed #736 for the CI part, but I don't know how to enable that. Happy to come back to this with a PR to fix the build issues once 6.2 comes out (feel free to remind me).